On august 15, calvin offers to sell clarissa his laptop for $500 cash. he tells clarissa she can only accept the offer by mailing the money to arrive by september 2 at his university mailbox. clarissa mails a check for $500 to calvin, and the money arrives in the mailbox by august 30th, although calvin doesn't retrieve his mail (along with clarissa's payment) until september 4th. did clarissa accept calvin's offer?