Read the following cases and answer all questions based on the US law:

Question (1):

Mark sent the below offer to Michel via email.

Dear Michel

This is Mark the owner of the red BMW. This amazing car does worth $6000. However, I am offering you to buy this car for $5000. This offer is stands for 3 days starting from the date of this email. If you wish to buy the car and accept this offer, please reply in writing to this email.

Looking forward to hear from you.

Regards,

Mark.

Michel replied to the email as follows:

Dear Mark,

Thank you for your email. I believe that this car is awesome and I am keen to purchase it. I accept your offer but I will pay you $4700 as I have to pay government fees and insurance.

I will visit you tomorrow to finalize all related documents.

Best,

Michel.

A. Do you think the deal is settled? Why or why not? Please state the rule that led you to your answer. 

B. If Michel replied to that email after 5 days from the day he received it and agreed to pay $5000, is the agreement still valid? State the rule that support your answer.