Bradford wanted to sell a certain parcel of land to Prince. He decided to make an offer by sending Prince a letter. When Prince received the letter, he decided to accept. He wrote a letter to Bradford saying that he would buy the land at the price quoted in the letter. Prince then mailed the letter. Before he received the letter from Prince, Bradford changed his mind and withdrew the offer to Prince. When Prince found out Bradford would not sell the land to him, he sued. Was Prince's letter a valid acceptance, binding Bradford to the sale? Explain.

What is the definition and/or elements of the legal concept being discussed?