On July 27, 2012 Summerson sent Fallson a letter offering to sell Fallson a vacation home for $150,000. On August 2, 2012 Fallson replied by mail agreeing to buy the home for $145,000. Summerson did not reply to Fallson. Do Summerson and Fallson have a binding contract?
a. Yes, because Summerson's silence is an implied acceptance of Fallson's letter.
b. No, because Fallson failed to sign the letter that was sent by Fallson.
c. No, because Fallson's letter was a counteroffer.
d. Yes, because Summerson's offer was validly accepted.