Mae and Rocco make a verbal agreement for Mae to buy Rocco's house for $250,000. Mae asks if Rocco can give her something in writing so she can apply for financing, and Rocco gives her a signed letter that says "I hereby agree to sell my house at 1164 Morning Glory Circle to Mae." The next day, Rocco gets an offer from Charlie, who is willing to pay $300,000 for the house. If Rocco sells the house to Charlie instead of Mae, will he be breaching a contract?