This rule can be illustrated in an example where A makes an offer by mail to sell land to B. The next day, A decides to revoke the offer and A therefore puts a letter in the message to B revoking the offer. Before the revocation offer reached B, B sent a letter accepting the offer to A. The revocation letter issued by A only reached B after the acceptance letter was sent. In this example, A cannot revoke the offer because B has already accepted the offer. There is a contract formed at the moment the letter of acceptance is posted, regardless of whether the letter comes to the attention of A, the