P sold Isokappacase to D from August 1981 until February 13, 1984. The label on Isokappacase indicated that the product was a 'starter media, a bacteriophage preventive medium.' Because Isokappacase contained more than 75% caseins or protein, its composition was characteristic primarily of a yield enhancer. D introduced the Isokappacase directly into the cheese milk to enhance cheese yields from milk but did not label its final product as imitation cheese as required by federal standards. P was aware of the fact that D's extremely large volume purchases of the product could only be accounted for by D's use of Isokappacase as a yield enhancer. When D stopped using Isokappacase as a yield enhancer, PTX stopped making the product. The trial court held the contract 'illegal and unenforceable' and ruled for D. P appealed.