(concurring in part, dissenting in part).
I disagree with the majority as to the award of prejudgment interest. I do not believe that the damages are certain or are capable of being made certain by calculation.
The majority’s reliance on Beka v. Lithium Corporation, 77 S.D. 370, 92 N.W.2d 156 (1958), is inapposite. In ruling that the plaintiff was entitled to damages, the majority in Beka stated: “That an established or reasonably ascertainable market price for loading and hauling the ore from the stockpile to the mill existed, is apparent from the record. In determining this the court did not have to select from conflicting evidence.” 77 S.D. at 376, 92 N.W.2d at 160. Moreover, plaintiff’s testimony was entirely uncontradicted.
Here, the trial court had not established or reasonably ascertained market values upon which to base its decision. On the contrary, the trial court, faced with a maze of conflicting evidence, arbitrarily placed a valuation on the work completed by the parties. Under these circumstances, the trial court’s award of prejudgment interest was clearly erroneous. In State v. Ed Cox and Son, 81 S.D. 165, 180-181, 132 N.W.2d 282, 290-291 (1965), we stated:
As we indicated in Beka v. Lithium Corp. of America, 77 S.D. 370, 92 N.W.2d 156, the person liable is in default for not paying interest only when he knows or can readily ascertain the exact sum of his indebtedness by computation. Even assuming that the defendants had admitted coverage under their bond they could not have known the extent of their liability until that was determined by the court.
In this case, at the time of trial appellant had no idea as to its liability or the extent thereon, nor does it as I now write. Appellant will know the extent of its liability for the first time when this decision is handed down. The reason for denying interest on a claim is that, where the person liable does not know what sum he owes, he cannot be in default for not paying.
*425In Peter Kiewit Sons’ Co. v. Summit Construction Co., 422 F.2d 242, 273 (8th Cir. 1969), we held:
In State ex rel. Farmers State Bank v. Ed Cox & Son, 81 S.D. 165, 132 N.W.2d 282 (1965) the court refused pre-verdict interest where the principal amount in dispute was the value of work performed under a construction contract. The court did not purport to retreat from the rule in Beka but found that the defendants could not have known the extent of their liability under the circumstances therein.
In the case at Bar (also a construction contract case) the parties could not have known the amount of their respective liabilities. The circumstances of the case precluded such a determination.
The trial court awarded judgment to ap-pellee in the amount of $51,015 principal on February 13,1980. Appellee, however, sued appellant for $76,412.58 on July 29, 1977. Appellee’s exhibit #43, dated August 31, 1976, reflects $65,849 as the “gross amount earned to date.” It is, therefore, most difficult for me to determine the date that a certain amount of money “vested” on a particular day. For this additional reason, I am constrained to dissent on the award of prejudgment interest.
I am authorized to state that Justice FOSHEIM joins in this concurrence in part and dissent in part.