Bart submits an offer to landscape Lisa's yard for $3,500. The next day, Bart decides that his price was too low and mails a letter to Lisa revoking his offer. Bart states in the letter that he is still willing to do the work for $4,000. Before Lisa receives Bart's letter, she calls Bart to accept his first offer. Bart states that it is too late; he has revoked that offer, but he will consider her call to be an acceptance of his second offer. HAVE BART AND LISA ENTERED INTO A CONTRACT? IF SO, ON WHAT TERMS? EXPLAIN YOUR REASONING. (5 points)