at least 10 points

Mr Alex sent a letter on January 12th to Ms Megan offering to sell his house for $250.000, stating that the offer was open only until January 20th Ms Megan received the letter on January 14th and prepared a letter of acceptance on that day, but had not mailed it. The next morning Mr Alex called Ms Megan and said that he has changed his mind and was withdrawing his offer. In accordance with the principles of law of contract and cases, discuss if there is a contract between Alex and Megan