A manufacturer of disposable foam products entered into a written contract with a take-out restaurant to sell them 5,000 disposable foam food containers per month at 5 cents per food container for a two-year period. Per the contract, payment of $250 was due once a month. The restaurant was also responsible for paying shipping charges, which were payable on a quarterly basis. Finally, the contract stated that if any of the containers were discovered to be damaged, they could be returned for a full refund. However, the contract was silent with regard to the return of any containers that were not damaged. In the last month of its contract with the manufacturer, the restaurant decided to switch to biodegradable, recycled cardboard food containers because its take-out customers complained about the harmful effects of disposable foam products on the environment. The restaurant asked the manufacturer not to ship the final shipment, but the manufacturer refused. The restaurant had not yet made the $250 payment for the final shipment of containers, but it did owe the manufacturer delivery charges for its final quarter. The restaurant returned all of the containers to the manufacturer. In addition, the restaurant sent an envelope with cash for the final shipping charges. In the envelope, the restaurant included a brief memo stating that the cash included was for payment in full, including all food containers and shipping charges. The manufacturer's accounting department received the envelope, read the memo, and deposited the cash. The manufacturer then sued the restaurant for the final payment of $250. Which of the following legal concepts would be the strongest argument against payment of $250? A. Novation
B. Good-faith modification
C. Estoppel
D. Accord and satisfaction