ON APPELLANT’S MOTION FOR REHEARING AND TO STRIKE APPEL-LEE’S REPLY TO THAT MOTION
Appellants H.S. “Gus” Edwards, et al. (Edwards) move the Court to withdraw its *573opinion and judgment of December 30, 1988, to grant reargument and rehearing, and to render judgment in their behalf. In numerous points of error, appellants claim this Court erred in finding that they were not entitled to monthly price escalations, state severance tax reimbursement or attorney’s fees under the terms of the contracts for the sale of natural gas by them to appellee Lone Star Gas Company, a division of Enserch Corporation (Enserch). For the below reasons, we believe our prior holding remains the correct one and, therefore, overrule Edwards’ motion for rehearing.
In their first point, Edwards argue this Court erred in finding that the contracts did not provide for monthly escalations. Edwards complain we wrongly interpreted the holding of the Houston Court in Enserch Corp. v. Houston Oil & Minerals Corp., 743 S.W.2d 654 (Tex.App.—Houston [1st Dist.] 1987, writ denied). This Court held the contracts at issue in this case differed from that in the Houston case because the present contracts defined the time for calculating the redetermined price. In fact, the Houston Court specifically recognized that monthly escalations were not “inconsistent with the express terms of the parties’ contract.” Id. at 656. The contracts at bar define the time for calculating the redetermined price as “the highest price per MMBTU to be paid as of the first day of the period for which the redetermi-nation price will be effective....” The Houston case was based on materially different language from the “annual” escalation language in the contracts at bar. That materially different language evidenced a different objective of the parties to that contract, i.e., to be bound by a market price value determined by third parties by reference to two contracts to find the “highest unit prices eligible for payment.” Id. at 657.
As to Edwards’ argument that this Court’s holding is inconsistent with Houston Oil & Minerals v. Enserch Corp., 732 S.W.2d 419 (Tex.App.—Houston [14th Dist.] 1987, writ ref’d n.r.e.), we find that case inapposite. That case did not involve the construction of a price redetermination provision, but, rather, a contract provision that provided for a one-time adjustment to the parties’ contract in the event the Federal Power Commission asserted jurisdiction to regulate the price at which the gas subject to the contract could be sold. Those facts are not analogous to those at bar. Edwards’ first point on rehearing is overruled.
In their second point, Edwards again complain that Enserch should be held responsible for reimbursement to Edwards for state severance taxes. Based on a theory of “incorporation by reference,” Edwards again contend that the present contracts’ language “referred to” the terms of other contracts and thereby incorporated all terms of those referenced contracts by implication.
Again, we stress the importance of looking to the contract for plain, clear and unambiguous language so that the contract may be given a certain or definite legal meaning or interpretation. Stahl Petroleum Co. v. Phillips Petroleum Co., 550 S.W.2d 360, 368 (Tex.Civ.App.—Amarillo 1977) (on motion for rehearing), aff'd, Phillips Petroleum Co. v. Stahl Petroleum Co., 569 S.W.2d 480 (Tex.1978). Any obligation to reimburse state severance taxes is lawful only to the extent permitted by the parties’ contract, Enserch Corp. v. Houston Oil & Minerals Corp., 743 S.W.2d at 658, and by specific provision in article XIII, Taxes, the parties in this case contractually agreed that seller, Edwards, would pay all taxes, including state severance taxes. Reference to the third party contracts for determination of a market value did not incorporate the terms of said contracts into the parties’ contracts. Edwards’ second point on rehearing is overruled.
In points three and five, Edwards argue this Court applied erroneous rules of contract construction. Edwards contend this Court did not consider their evidence of commercial and regulatory circumstances, did not give effect to all the relevant contract provisions or to course of performance evidence and, finally, that our construction of the contracts is inconsistent *574with federal and constitutional law and is incorrectly based on public policy grounds.
Contracts that can be given a definite legal meaning by construing the language used by the parties will not be rendered ambiguous or be subject to change on the basis of parol evidence. Universal C.I.T. Credit Corp. v. Daniel, 150 Tex. 513, 243 S.W.2d 154, 157 (1951). The contract at bar specifically allows an “annual” redeter-mination, definitely determining the time for the escalation of price. The instant contracts contain no “incorporation by reference” language, and in fact, specifically provide that reference is made to third parties’ contracts to establish “the highest price per MMBTU to be paid as of the first day of the period for which the redetermined price will be effective.”
We remain convinced, and the parties continue to agree, that the contracts are unambiguous. Therefore, we continue to believe that a strict construction of those terms is the appropriate application. Edwards’ third and fifth points on motion for rehearing are overruled.
In their sixth point, Edwards argue this Court erred by failing to consider the “extensive argument and authorities [they] presented to complain of the trial court’s partial award of attorney’s fees and expenses.” Due to our determination that Edwards take nothing in this case, the question of whether the trial court erred in failing to correctly determine questions of attorney's fees is moot. See Mollinedo v. Texas Employment Ccm’n, 662 S.W.2d 732, 738 (Tex.App.—Houston [1st Dist.] 1983, writ ref’d n.r.e.); Grant v. Grant, 358 S.W.2d 147 (Tex.Civ.App.—Waco 1962, no writ). Edwards’ sixth point is overruled.
In its fourth point on motion for rehearing, Edwards argue this Court erred in rendering judgment for Enserch on prices paid from and after April 1, 1984. Edwards acknowledge that the trial court “never found it necessary to rule on this specific claim because the trial court granted Edwards the full fluctuating section 102 prices through the end of the contract in October 1985.” Edwards then request this Court to decide that claim on rehearing and to “render the judgment the trial court should have rendered.”
Having acknowledged that this issue was not presented to the trial court for determination, Edwards cannot now complain at the appellate level. Roling v. McGeorge, 645 S.W.2d 886, 888 (Tex.Civ.App.—Tyler 1983, no writ); Vendig v. Traylor, 604 S.W.2d 424, 430 (Tex.Civ.App.—Dallas 1980, writ ref d n.r.e.). Edwards’ fourth point is overruled.
Having overruled all of Edwards’ points on motion for rehearing, we continue to believe our original judgment in this case is the correct one, and, therefore, overrule Edwards’ motion for rehearing in the matter.
Appellants have also filed a motion to strike appellee’s reply to their motion for rehearing. In that motion, they acknowledge that appellee received a copy of the motion and its supporting documents on January 18, 1989. Texas Rule of Appellate Procedure 19(a) provides that a response to a motion may be filed within 10 days after service of the motion, unless the court has shortened or extended the time for filing that response. The tenth day after service of the motion in question was Saturday, January 28,1989. Texas Rule of Appellate Procedure 5(a) provides that the day upon which a designated period of time begins to run is not to be included. The last day of the period, however, is to be included unless it is a Saturday, Sunday, or legal holiday in which event the period runs until the end of the next day which is neither a Saturday, Sunday, nor legal holiday. In their motion, appellants acknowledge the filing of the response on Monday, January 30, 1989. Therefore, even under appellant’s computation, the response was timely received. Moreover, and parenthetically, under Texas Rule of Appellate Procedure 100, no response to a motion for rehearing is required. Appellants’ motion to strike the response is also overruled.