Wayne Helped Hank Study All Night for an Important Exam

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."

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