Mary offered to sell John her antique furniture at a very good price. John could not accept the offer at that time, but did give Mary $225 in return for her promise to keep her offer open for an extra three weeks. John returned with the agreed-upon balance one week later to find that Mary already sold the furniture she had offered to sell him. Mary said that because the furniture pieces were all antiques and that she had not heard from John, she sold her furniture to another buyer who was willing to pay more money than John. She offered to return John’s $225 plus an additional $50 for the inconvenience and insisted that this was all she was obligated to do. Was Mary right? Please explain why or why not.