Wayne Helped Hank Study All Night for an Important Exam

Multiple Choice

Wayne helped Hank study all night for an important exam.After Hank got an "A" on the exam,he told Wayne,"I will give you $10 for helping me get a good grade." Wayne said,"Thanks,I'll take it." There is:

A) no contract because there is no mutual assent.
B) no contract because there is no valid consideration.
C) no contract because $10 is reasonably inadequate consideration.
D) a contract with sufficient consideration.