Abner tells a representative of Brass & Woodwind Musical Instruments, Inc., that he will pay for Claudia's trumpet if she does not. Abner does not secure any personal benefit for this promise. This promise is enforceable as a contract:

a.only if the value of the trumpet is more than $500.

b.under any circumstances.

c.only if it is in writing.

d.only if Claudia agrees to it.