Mary Bought a New Macintosh Computer and Advertised Her Old

Mary bought a new Macintosh computer and advertised her old computer system for $1500.Mr.Jones offered to pay $1000.Mary said no,she wanted $1500.Mr.Jones offered $1250.Mary rejected that and said she wanted $1500 but then said to him,"I withdraw my offer,I've decided to give it to school and apply for the tax benefit." Mr.Jones said,"All right,I'll accept your offer of $1500." Which of the following is true?

A) There is a contract because at some point in time Mary was willing to sell and Mr. Jones was willing to buy the computer system for $1500.
B) There is no contract because the last offer had lapsed.
C) There is no contract because Mary revoked the offer before Mr. Jones attempted to accept it.
D) There is a contract, because once a seller makes an offer she cannot change her mind; she is bound to receive an acceptance.
E) There is a contract and Mr. Jones has to pay a reasonable price for Mary's old computer.