Joe's Car Is for Sale and He Tells Tom That

Joe's car is for sale and he tells Tom that Tom can buy the car for $9,000 if he lets him know within that week. Joe later changes his mind and writes a letter to Tom, which he mails. Five minutes after Joe mails the letter, he receives a phone call from Joe accepting the offer to buy the car. Does Joe have to sell Tom the car?

A) Yes, because the offer stated it would be open for a period of time and it was accepted before the revocation reached the offeree.
B) Yes, because an offeror is master of his offer and can revoke it at any time.
C) No, because an offeror is master of his offer and can revoke it at any time.
D) No, because Tom only called and did not come with the money for the car.
E) No, because the mailbox rule says that a revocation becomes valid when it is mailed.