Tom Contracts with Susan to Build Her a Shed for $6,000,payable

Multiple Choice

Tom contracts with Susan to build her a shed for $6,000,payable on July 1 when he expects to complete the shed.Tom has assigned his right to payment to National Bank in order to obtain building materials.On July 1,National Bank tries to collect the money from Susan,but she refuses because Tom has not completed the shed.What is the result?

A) Susan must pay Tom on July 1.
B) Susan must pay National Bank on July 1.
C) Tom must pay National Bank on July 1.
D) Susan does not need to pay National Bank until the shed is complete.