Please clarify the solution of all parts of the following problem
Problem- Returned before 4:00, saw Debbie carrying the books and said to Sally, "You can't sell those books to her! We had a deal!" Although he attempted to give Sally $100, she refused the money.
Betty arrived shortly thereafter, and showed Sally the shoes and purse that she had purchased to go with the gown. Sally told her the evening gown had been sold.
Part 1- Does Andy have an enforceable contract with Sally? Discuss.
Part 2- Does Betty have an enforceable contract with Sally? Discuss.
Part 3- Does Chuck have an enforceable contract with Sally? Discuss.
I want help to explain the enforceable contract between Andy and Sally.