Jim's Contract with Frank Obligated Jim to Pay Frank $10,000

Multiple Choice

Jim's contract with Frank obligated Jim to pay Frank $10,000.Frank properly assigns the contract to Abel.At that time,Abel notifies Jim about the assignment.Jim,however,forgets and pays the $10,000 to Frank.By this time,Abel is screaming for his money.However,by then,Frank goes into bankruptcy.In this case:

A) Jim is liable to Abel for $10,000.
B) Abel is out of luck because Jim performed his obligation by paying Frank.
C) Jim is liable to Abel not for the $10,000,but for his breach of the implied warranty that the assignor is solvent.
D) Abel is out of luck because his notification was oral rather than written.