On 10 March 2022, David sends a letter to Judy offering to sell his used Toyota Camry for $15,000. Judy receives the letter on 13 March 2022, and accepts this offer in a letter which she posts to David on 14 March 2022. However, on 11 March 2022, David has a change of heart and sends Judy a letter revoking his original offer. Judy receives this letter of revocation on 15 March 2022. David telephones Judy on 15 March 2022 to confirm his change of mind that he does not want to sell his car. Judy tells David that his change of heart is too late since they have already entered into a binding contract. Is Judy correct? If there is a binding contract, on which date was this formed? Is David's letter of 11 March 2022 a valid revocation of his offer? Your Task: Advise Judy whether she can enforce her claim against David. Your advice must be substantiated based on the common law rules regarding "agreement", with clear reference to relevant cases.