Cindy Nanson had a contract with Bob Greenly for Bob to repay Cindy $2,000 plus interest by July 1980. It is now August 1990 and Cindy has not received any payment. Cindy wishes to file suit to collect the $2,000. Bob reminds her that the statue of limitations for contract suits is four years. Cindy's contract with Bob is:
a. unenforceable.
b. void.
c. voidable.
d. all of the above.