Bob Signed an Agreement with Joe Under Which Bob Agreed

Bob signed an agreement with Joe under which Bob agreed to purchase all the hay that Joe grew during the coming growing season.This contract will be:

A) unenforceable due to its vagueness.
B) unenforceable due to the difficulty of devising an appropriate remedy for a breach.
C) enforceable as long as both parties act in good faith and Bob doesn't suddenly demand more hay than what was reasonably estimated.
D) No contract was formed as the quantity term was indefinite.