On September 1, Jennings, a used-car dealer, wrote a letter to Wheeler in which he stated, "I have a 1955 Thunderbird convertible in mint condition that I will sell you for $13,500 at any time before October 9. [Signed] Peter Jennings." By September 15, having heard nothing from Wheeler, Jennings sold the Thunderbird to another party. On September 29, Wheeler accepted Jennings's offer and tendered $13,500. When Jennings told Wheeler he had sold the car to another party, Wheeler claimed Jennings had breached their contract. Is Jennings in breach? Explain.