Bill Recently Borrowed $50 from Ricardo for a Couple of Weeks

Multiple Choice

Bill recently borrowed $50 from Ricardo for a couple of weeks. Bill, still short of cash, tells Ricardo, "I will wash and wax your car in exchange for the $50 I owe you." Ricardo tells Bill, "OK, that's great!" Ricardo's performance of his new duty will be:

A) an accord.
B) a novation.
C) a rescission.
D) a satisfaction.