Patricia makes a written offer to Ted to sell her car for $10,000. In her offer, she states that "this offer will remain open for 5 days". Two days latter she tells Ted she has changed her mind.

question: advise Ted under the law of contract, whether he can still accept the offer and hold Patricia to the sale.

I think Ted has accepted when he received the offer, which means they have a valid contract with each other in this offer.

so, if they have a valid contract, the offer can be canceled only before the offeree acceptance.

In thiscase, Ted has already accepted the offer and it will remain 5 days, so Ted can still accept the offer and hold Patricia to the sale.

But I am not sure I am right. Please give me more detailed information.

Thank you!