Joc Oil bought a cargo of fuel oil for resale. The certificate from the foreign refinery stated the sulfur content of the oil was 0.5 percent. Joc Oil entered into a written contract with Con Ed for the sale of this oil. The contract specified a sulfur content of 0.5 percent.

Joc Oil knew, however, that Con Ed was authorized to buy and burn oil of up to 1 percent sulfur content and that Con Ed often bought and mixed oils of varying contents to stay within this limit. The oil under contract was delivered to Con Ed, but independent testing revealed a sulfur content of 0.92 percent.

Con Ed promptly rejected the nonconforming shipment. Joc Oil immediately offered to substitute a conforming shipment of oil, although the time for performance had expired after the first shipment of oil. Con Ed refused to accept the substituted shipment. Joc Oil sues Con Ed for breach of contract. Judgment?