Leo made an offer to Mel on Monday, but on Tuesday Leo mailed Mel a letter revoking the offer. On Wednesday, Mel accepted the offer by phone. Mel received the letter revoking the offer on Thursday. There is no contract because the offer was revoked on Tuesday, before Mel's acceptance. O A contract was formed under the "mailbox rule." A contract was formed because the acceptance took place before the revocation was received. O None of the above