Penny has a student loan with an outstanding balance of $5,000. She sends in a check for $3,000 and writes in the memo section "PAID IN FULL." The lender cashes the check. Penny refuses to pay any more money on the loan, claiming that a binding contract for $3,000 was created when the lender cashed the check. The lender sues Penny. Decide who wins and explain why, making sure your answer includes a benefit/detriment analysis.