On May 1, 1972, Mix, CPA, entered into an oral contract with Dell to provide certain accounting services to Dell. The contract was fully performed by both parties in 1974. On April 25, 1988, Dell commenced a breach of contract action against Mil claiming that Mil had improperly performed the accounting services. Mix's best defense to the action would likely be the
a. Parol evidence rule
b. Statute of limitations
c. Statute of frauds
d. Lack of consideration