Answer:
Jennings breached the contract
Explanation:
A merchant firm offer is one that is irrevocable, the offeror makes an offer to sell goods within a given time frame and signs off on it.
Even without consideration (acceptance) from the other party, the contract is irrevocable.
A merchant firm offer that does not have a stated time frame rains open for a reasonable time.
In this instance Jennings made a merchant firm offer. Even if Wheeler had not accepted the offer it is irrevocable till June 9.
So by selling the car on May 15 he has breached the contract.