In this action for breach of contract, defendant appeals from a judgment entered pursuant to a jury verdict.1 We affirm on the appeal. Plaintiff cross-appeals and seeks prejudgment interest on the jury’s award of $11,000 for the amount due on the “balance of the employment contract.” Plaintiff alleged in his amended complaint a foundation for prejudgment interest from January 15, 1979. The $11,000 which plaintiff sought to recover from defendant was ascertained or readily ascertainable by simple computation. See Krieg v. Union Pacific Land Res. Corp., 269 Or 221, 234, 525 P2d 48 (1974). Accordingly, plaintiff is entitled to prejudgment interest at the legal rate2 commencing January 15, 1979, for each installment as it fell due under the contract. See, e.g., Kotan v. School Dist. No. 110C, 13 Or App 139, 149, 509 P2d 452 (1973).

Affirmed on the appeal; reversed on the cross-appeal; and remanded with instructions to enter a new judgment not inconsistent with this opinion.