Defendant Gulf and Western (“G & W”) appeals from a jury verdict for plaintiff Coal Resources, Inc. (“CRI”) in CRI’s diversity breach of contract action against G & W raising numerous evidentiary issues.1 CRI cross-appeals the District Court’s denial of pre-judgment interest. We REMAND to the District Court for a new trial unless CRI remits $226,563 of the awarded damages.
I.
This is the third time this case has been tried and appealed to this Court. The case has been considered on original appeal, a rehearing of that appeal, an appeal following a second trial and now this appeal following the third trial. The basic facts of the case were adequately related in the opinion addressing the second appeal and we quote from that case:
Coal Resources, Inc. (CRI) obtained leases on coal properties in Virginia and Kentucky and began mining operations in the early 1970s. The leases required CRI to “diligently mine” the properties and to pay minimum royalties to the lessors regardless of the amount of coal mined. In 1975, CRI entered into negotiations for the sale of its assets to defendant Gulf & Western (G & W). On July 11, 1976, the parties reached an agreement. CRI’s assets were transferred to G & W subsidiaries Virginia Met Coal Company and Jersey Kentucky Coal Company. G & W paid CRI $2.1 million, promised to pay $500,000 one year after the date of the sale on a promissory note CRI owed to a bank, assumed CRI’s equipment debt of $1.7 million, and agreed to pay CRI 2.8 times any annual adjusted net profits (“the multiple”) of Virginia Met Coal Company for the two years following the sale after deduction of certain amounts already paid and with a maximum limit of $11,666,000. In a separate agreement G & W also assumed CRI’s obligations under the leases.
After acquiring the leases, G & W was unable to mine the leased property profitably. Eventually G & W lost the leases either through failure to pay minimum royalties to the lessors, through litigation settlements with its contract miner, or through voluntary surrender. No money was ever paid to CRI under the multiple because Virginia Met Coal operated at a loss. CRI then brought suit.
In 1981, following the first trial in this case, the jury found G & W liable for breach of contract, promissory fraud, and securities fraud. The jury awarded CRI more than $17 million in compensatory damages, and more the $11 million *1265in punitive damages and attorneys fees. The trial court ordered a remittitur to $12,050,000 and granted G & W’s motion for judgment notwithstanding the verdict on the securities claim.
On appeal, this court affirmed originally the judgment dismissing the securities law claim, reversed the judgment on the other claims and remanded those claims for a new trial. CRI then filed a petition for rehearing which was granted. Following supplemental briefing, the original hearing panel affirmed the j.n.o.v. on the securities law claim, reversed the judgment for CRI on the promissory fraud claim, vacated the judgment for CRI on the contract claim, and remanded for a new trial [in that claim]. Coal Resources, Inc. v. Gulf & Western Indus., Inc., 756 F.2d 443 (6th Cir.1985).
Coal Resources, Inc. v. Gulf & Western Indus., Inc., 865 F.2d 761, 764-65 (6th Cir.1989). At the second trial the jury again found in favor of CRI on the contract claim and returned an award of $7,850,000.
On appeal, this Court reversed the judgment of the District Court on the contract claim and once again remanded the case for a new trial. The Court found that the testimony of plaintiffs’ expert witness was too speculative in some respects to be admissible and that the defendants had been unfairly treated by the denial of a witness. At the third trial, the jury again found for CRI on the contract claim, awarding damages of $8.9 million. At this third trial, G & W admitted breach of the contract to mine diligently. Thus, the only issue tried was damages.
G & W appeals claiming that CRI openly defied this Court by basing its case on the same testimony and expert this Court found to be speculative in 1989. Coal Resources, 865 F.2d at 761. G & W claims that CRI’s testimony is inadmissible speculation under the “law in the case” doctrine and that as a result final judgment should have been rendered for G & W. G & W further contends that the trial court erred in excluding evidence of coal prices presented by its witness. CRI cross-appeals claiming that the trial court erred in denying pre-judgment interest.
II.
We first must decide whether the District Court and the parties in this case allocated appropriate weight to this Court's previous holdings. G & W asserts that CRI ignored the 1989 ruling of this Court which held that the expert testimony given by Coal Resources’ experts, primarily Stonie Barker, was too speculative to be admissible. Coal Resources, 865 F.2d at 770. G & W argues that admission of testimony by the same expert at the retrial openly defies the previous rulings. Further, G & W contends that it is “law of the ease” that CRI’s damage theory is inadmissible speculation. During the course of the third trial, the defense objected to the testimony by Stonie Barker. When denying the motion, the District Court stated:
I acknowledge that the Court of Appeals rejected Mr. Barker’s testimony as too speculative to be admissible on retrial. The Court finds that this is a different trial than the one perceived by the Court of Appeals in the last case. There are many — there have been some changes in it, particularly the stipulations of the defendant.
Joint App. at 2487.
The law of the case doctrine “precludes this Court from rehearing a previously decided issue unless one of three ‘exceptional circumstances’ exists [including] that the evidence in a subsequent trial was substantially different.” 865 F.2d at 767 (quoting Kori Corp. v. Wilco Marsh Buggies & Draglines, Inc., 761 F.2d 649, 657 (Fed.Cir.1985). Thus, CRI may use similar testimony at the second trial where that testimony is now supported by new evidence presented by either the plaintiffs or defendants. The defendants’ position on many issues did change since the earlier trials. Although G & W do not agree with CRI on every issue, the disagreements between the parties now center on five issues.2 Clearly, CRI still must provide some basis from which a jury could find that the witness’ estimates had foundation and the opinions were grounded in reason. That the previous testimony was speculative does not now preclude Barker’s testimony where a *1266foundation for it is supplied. Barker’s testimony is admissible since both G & W and CRI submitted substantially different testimony. G & W argues that this exception should not apply because Stonie Barker’s testimony has remained the same. It is true that Barker’s opinion is largely the same. However, there is no requirement that Barker’s specific testimony must change; a change in the other testimony and evidence presented at trial which provides support for Barker's testimony removes the impediment of speculation.
III.
This Court’s review of a civil jury verdict must determine if the verdict “is sufficient to support the judgment, [and] follow the traditional rule of viewing the evidence in the light most favorable to the prevailing party.” Coal Resources, 865 F.2d at 767. Damages which are remote or speculative are not permitted. Grantham & Mann, Inc. v. American Safety Prods., Inc., 831 F.2d 596, 601 (6th Cir.1987). Further, “[o]nce the existence of damages has been shown, all that an award of damages requires is substantial evidence in the record to permit a factfinder to draw reasonable inferences and make a fair and reasonable assessment of the amount of damages.” Id. at 602.
The defendants continue to complain that several of the assertions made by Barker and other plaintiff witnesses amount to inadmissible speculation. A Study Team (“Team”) commissioned by G & W presented a property development report dated February 19, 1990. This report together with the testimony and evidence submitted by both sides narrow the areas of disagreement to five. We limit our discussion to issues still subject to disagreement which are not clearly waived by the defendants.
A. Percentage Of Coal Which May Be Sold As Metallurgical Coal
This Court noted at the last appeal that the percentage of steam coal and metallurgical coal produced by the mine was material. Coal Resources, 865 F.2d at 771. G & W warrants that CRI has failed to show any factual basis in the record for Barker’s assumption that more than 60% of the mined coal could be sold in the metallurgical market. Barker’s plan assumed that the mix of coal sold during the multiple years would be 80% metallurgical and 20% steam. G & W’s plan allows that while the coal may be produced at that ration, only 60% of the coal could be sold as metallurgical coal.3 G & W believes that the 80%/20% sales ratio could not be achieved until the mine was established as a reliable producer of metallurgical coal and the new coal plant was completed. The testimony of G & W’s experts provides credibility to Barker’s assumed coal mix. In addition, subsequent to the last appeal Humphreys Enterprises opened up deep mines on the Kelly seam on this property and thus new information is available concerning the type of coal mined and the time needed to mine the coal. The testimony of all the witnesses in this area provides an adequate foundation for the jury to infer that 80%/20% was a reasonable ratio to use in determining damages.
B. Prices
In his mining plan, Barker assumed selling prices for metallurgical coal of $44.00 and $42.00 for the first and second years of the multiple respectively. He assumed a price of $34.00 for steam coal both years of the multiple. Defendants assert that there is no evidence that these prices could be obtained. Rather, the Team report for G & W indicated metallurgical coal prices of $34.00 and $35.00 for multiple years and a steam coal price of $24.00. Various defense witnesses testified concerning other prices obtained for specific sales. G & W argues that Barker ignores the actual sales prices obtained for the best coal on the property and used a higher price in his projections than could have been possibly attained.
CRI presented two experts, Stonie Barker and Charles P. Eddy, on the issue of coal sale prices during the multiple years. Defendants do not challenge either expert’s qualifications to testify on this issue. Both Barker and Eddy declared that their price estimates were based on personal knowledge of coal prices during the multiple *1267years and gave similar price estimates.4 Barker also introduced and relied on a long-term contract report of his former employer, Island Creek, that showed negotiated prices for metallurgical coal which went into effect April 1, 1976. Joint App. at 2901, 4351. Barker’s steam coal price estimates were based on personal recollection and further supported by a letter from Lloyd Evans, president of Island Creek, outlining steam coal prices during 1975-1977.
Our decision on the last appeal criticized Barker’s testimony on prices because they were based on a small number of small sales. During the third trial, however, Barker’s testimony was reinforced by Eddy’s testimony. Eddy based his estimates on large purchases his company made during the multiple years. This testimony, combined with Barker’s expanded testimony, can no longer be considered speculative. We believe that a jury could reasonably use Barker’s price estimates in determining damages.
G & W also protests the trial court’s refusal to allow G & W to present evidence of spot market prices during the multiple years. Stanley Ringstaff, who testified about large numbers of spot market sales in which he had participated, was prepared to substantiate his testimony with notes he had taken concerning the sales. The District Court judge determined that the failure to admit Ringstaff’s documentation was harmless error. (Ruling on Defendants’ Motion for J.N.O.V. and/or New Trial.) A variety of witnesses gave evidence that sales prices ranged from $38.00 to $39.00 for metallurgical coal. These witnesses thus provided support for Ring-staff’s estimates. We believe that this supportive testimony makes the failure to admit the evidence on prices harmless error.
C.Return On Investment
During his testimony, Stonie Barker testified that 10 to 20 percent constituted a reasonable return on investment for a mine. Barker additionally testified that in an inflationary period returns of greater than 20% would not be unreasonable.5 G & W argues that Barker’s mine plan will result in a 100% after tax return on investment for the first year of the multiple. Defendants believe that such a return exemplifies the speculative nature of Barker’s testimony.
Defendants’ argument is based on an improper calculation of the return on investment. G & W’s calculation assumes that they incur no obligation to pay under the multiple. If the estimated profits under Barker’s mine plan were considered additional capital investment, the return on equity under Barker’s plan would be 30%. Presented together with the proper support, this return on equity could be viewed by the jury as reasonable.
D. Days Worked
In his mine plan, Barker assumed 262 working days in the first year and 191 days in the second year. No other expert, including CRI’s expert Eddy, assumed this high of a number of workdays. Documentation provided by the other experts, both G & W’s and CRI’s, indicate that mines in operation during this time averaged about 230 days.6 CRI defends Barker’s testimony by noting that the dispute really centers on whether the miners would have worked every other Saturday. The number of “down days” for unexpected events such as severe weather and interruptions outlined in both Barker’s and the Team’s plans differed by only five days. A jury could have reasonably accepted CRI’s argument that Virginia Met employees would have mined every other Saturday. We agree therefore with the District Court finding that the testimony and calculated damages were not speculative based on this issue.
E. Production Commencement
Barker’s mine plan assumes reduced production for the first month and then full scale production for the remainder of the multiple. G & W asserts that additional time would be necessary before deep mining would be possible. This time would be used to obtain permits, install electricity, *1268and conduct various studies. Witnesses Stagg and Peake testified that there was ready access to 1,150,000 tons of deep min-able coal, that engineering companies had surveyed the property and prepared a mining plan prior to closing, and that a report had been prepared outlining the feasibility and estimated costs of the mining. Stagg also testified that deep mining can begin during exploratory mining. This testimony, combined with other expert opinions, properly presented an issue which the jury had ample evidence to decide.
F. In-House Sales Force
Barker’s mining plans call for the coal to be sold through an in-house sales force. G & W defense expert, Stanley Ringstaff, testified that smaller businesses generally sell through brokers until they are established. However, Ringstaff further stated that “[A]s far as the conclusion of the team was that we would, after we built up production, that we would work toward an in-house sales force.” G & W’s other expert Evans testified that at the beginning of the multiple, G & W was selling through Vice President Cecil Peake and that such a system was common practice in the coal industry. Evans’ statement is supported by the Team report which stated that in-house sales were normal in the coal industry. These statements by defense experts lend support to Barker’s assumptions and form a basis for a reasonable decision by the jury.
G. Construction Of The Preparation Plant
A coal preparation plant washes and cleans deep mined coal prior to sale. Both the defendants and plaintiffs agree that the construction of a new coal washing facility was necessary to diligently mine the coal. The parties disagree, however, on the type of plant and the time necessary for construction. These factors are critical in the calculation of profit during the multiple years since the speed with which a plant is constructed and the associated cost directly impacts income during the multiple years. Defendants’ expert, Leo Haanskorf, asserts that a three-stage plant, with three separate cleaning systems, would have been appropriate. This plant would cost $1.5 million more that the heavy media cyclone modular plant suggested by Barker. The three-stage plant would also take four months longer to build than the modular plant. We believe that the issue of what type of coal preparation plant should be built was properly presented and argued to the jury. We do not believe, however, that CRTs expert was properly qualified to testify as to the cost of the chosen plant.
G & W contends that Barker is not qualified to testify concerning the cost associated with the construction of a coal preparation plant. Federal Rules of Evidence define an expert witness as one whose “knowledge, skill, experience, training, or education” gives the witness scientific, technical or specialized knowledge which will assist the trier of fact. Fed.R.Evid. 702. Barker was the Chief Executive Officer of Island Creek Coal. There is no dispute that he is qualified to give expert testimony about the development and mining of the property purchased by G & W. His qualifications as an expert on property development, however, do not automatically qualify him to testify concerning the costs and appropriateness of coal preparation plants. Amato v. Syntex Laboratories, 917 F.2d 24 (6th Cir.1990). CRI asserts that Barker approved and reviewed all coal preparation plant construction and modification during his tenure at Island Creek and should be considered qualified. Review of plans and budgets prepared by others differ substantially from the preparation and design of the plans. Thus, Barker could be considered qualified to choose the type of plant but this may not qualify him to give an expert opinion about the associated cost.
Barker’s testimony reveals that although he had been involved with the plant construction plans while Chief Executive Officer at Island Creek, “I had people on the staff who would make analysis of the kind of preparation plant you want for a given set of conditions, and of course they would submit those plans and the capital budget to me.” Further, Barker admitted, in reply to the question of whether he considered himself a coal preparation plant expert, “I leave that up to the people.” The modular single stage plant Barker recommends in his report was a newer innovative type plant in 1976. Barker states in his testimony that Island Creek Coal did not complete a similar plant until 1977. That plant was only used as a temporary facility and did not have the size or capacity of the plant Barker recommends in his report. There is no other evidence in the record that Barker was involved with the construction of another single stage coal preparation plant.
*1269Barker acknowledged that although he selected the plant type G & W should have used, he relied on others for the design and cost estimates for the plant. Barker supplied no records or documentation to support the cost estimates and none of the people who supplied the information appeared as witnesses.7 Because of these deficiencies, we find that Barker was not qualified to testify concerning the cost of constructing a coal preparation plant and the CRI has failed to otherwise prove the cost of the plant.
We do not believe a new trial is needed. However, to rectify the error in permitting Barker to express an opinion on the cost of such a plant, a decrease of the damage award to CRI is necessary. Haanskorf testified that Mr. Barker’s estimates for the heavy media cyclone plant underestimated the costs by $725,000. Joint App. at 3401. If this amount is added to Barker’s estimate, the new plant cost would be $2,025,000. Adjusting this plant cost for depreciation and interest, $226,563 should be subtracted from mine income in Barker’s prepared reports.8 Thus, a remittitur of $226,563 is warranted. An appellate court may permit or order a remittitur if the proper reduction to damages is ascertainable from the record. Hansen v. Boyd, 161 U.S. 397, 16 S.Ct. 571, 40 L.Ed. 746 (1896); Flame Coal Co. v. United Mine Workers of America, 303 F.2d 39 (6th Cir.), cert. denied, 371 U.S. 891, 83 S.Ct. 186, 9 L.Ed.2d 125 (1962). This power to reduce a verdict is conditional on the consent of the prevailing party. Washington and Georgetown R.R. Co. v. Harmon’s Adm’r, 147 U.S. 571, 13 S.Ct. 557, 37 L.Ed. 284 (1893). We therefore remand this case for a new trial unless CRI remits $226,563 of the verdict. If such an amount is remitted, the verdict will be affirmed.
IV.
The District Court denied a motion by the plaintiffs for an award of interest on the damage verdict. This Court can reverse this decision only if it finds an abuse of discretion. Coal Resources, 865 F.2d at 776. We find no such abuse.
CRI argues that G & W’s position in the 1990 trial contradicts their positions in the earlier trials, that their earlier claims were therefore false and frivolous, and that prejudgment interest should be awarded as a sanction. G & W did change its position as to whether its mining efforts could be considered diligent, but only after submitting the data to a new set of experts and receiving a different opinion. No evidence was produced which indicated that G & W knew that their mining was not diligent during the first trials. We find that the evidence does not clearly indicate conduct sufficient to require payment of pre-judgment interest and affirm the District Court’s decision denying the motion for pre-judgment interest.
Y.
For the reasons stated above, we REMAND the decision of the District Court for a new trial unless consistent with this opinion plaintiffs accept a reduction of $226,563 from the damages awarded. No costs are awarded since both parties have prevailed in part.
. The plaintiffs-appellees are identified collectively as Coal Resources, Inc. in the parties’ briefs, in the rulings of the lower court, and in the prior decisions of this Court, and will be referred to by that designation in this opinion. Similarly, Virginia Met Coal Company, Jersey Kentucky Coal Company and New Jersey Zinc Company are wholly-owned subsidiaries of Gulf & Western Industries. In the parties' briefs, the rulings of the lower court, and the prior decisions of this Court they have been treated as an entity and referred to as Gulf & Western. We will do the same.
. The Study Team hired by G & W to prepare a Property Development Report which estimated the profit that G & W would have achieved from diligent mining, filed a report stating: "[a]l-though we would argue about certain areas, it seems we can accept Stonie Barker’s position in all but five areas.” Exhibit 995. These areas were market price, reserve base, days worked, preparation plant type and timing, and deep mine start-up.
. G & W's expert, Lloyd Evans, stated during trial, "Mr. Barker and we really concluded about 20 percent of the strip coal would be oxidized to the point where it could not be sold as metallurgical coal.” Joint App. at 3534.
. Eddy estimated that metallurgical coal of slightly lower quality than defendants’ sold for $36.00 and $38.00 per ton before commission during the multiple years.
. G & W's Team plan results in a return on equity of just over 19%.
.Eddy, who was on the board of directors of a mine during the multiple, testified that 220 to 230 days of work would have been a satisfactory year. White Bourland, who operated three different mines during the multiple years, produced documents which indicated that these mines would have operated 232, 190, 228 days if no strike had occurred.
. We do not believe that this case is similar to a case where a doctor presents evidence on a patient illness and uses the results of tests and analyses conducted by other doctors and technicians. In those cases, the doctor relies on proven test methods and results to obtain information necessary to the treatment and care of a patient. In this case, Barker is relying on others to estimate the costs of an innovative project solely for the purposes of introducing these costs as evidence in litigation.
. As stated above, the adjustment in price of 1725,000 results in a new plant cost of $2,025,-000. This cost is then substituted in Barker's reports in the proper positions. The additional interest expense for the first fifteen months created by this adjustment totals $181,250 if Barker’s assumed rate of 20% is used. The additional depreciation for the first fifteen months, using Barker’s assumed rate of five percent per year, is $45,313. These sums are added, for a total of $226,563, and deducted from mine income.