The buyer contracted with the seller for the purchase of ribs. After delivery, the buyer refused to pay the contract price, claiming that the ribs arrived in an "off condition." The seller fi led suit for breach of contract. The buyer claimed that when the ribs were defrosted and thawed, they were unfit for consumption. The seller claimed that the off condition occur red after delivery to the buyer. Who had to prove what? Did the buyer have to show that the off condition occur red before taking possession? Or could there have been some kind of assumption after the meat was defrosted?