Jack of Grumpytown writes to Jill of Happyville on Wednesday, offering his hunter green Jaguar XJ for sale in the amount US$50,000. Jill receives the letter and calls Jack to accept the offer. Jack insists on getting the acceptance in writing before Friday (the same week) at 10:00am or else he would sell the vehicle to someone else. Jill immediately writes the letter of acceptance and posts it. Jack receives Jill's letter 9:00am on Friday morning. In the meantime, Jack has received a better offer overnight and has written to Jill telling her that he is going to sell the Jaguar XJ to someone else. He posted the letter on Thursday night at 8:00pm. Jill never received the letter. Please advise Jill. In your answer discuss the essential ingredients of a contract and use case law to substantiate your points.