Juan promised to sell his guitar to Casey who promised to pay him $1000. After Casey tendered the payment, Juan reneged on his promise, so Casey filed suit. Which of the follwoing is true? a. In a bilateral contract, each party is bound only if each receives a legal benefit and incurs a legal detriment. b. Casey cannot enforce Juan's promise because he neither incurred a legal detriment nor received a legal benefit. c. The contract is unilateral, so only Juan is bound. d. The consideration for Juan's promise is both a legal detriment to Casey and a legal benefit to Juan