Nick was reading the local paper when he came across an ad for a puppy. He called the owner and he said he would deliver the pup to his home. He gave the seller his credit card information over the phone and rushed out to purchase a few chew toys, a bed, and some food. When the doorbell rang, the owner had not delivered a puppy but a large dog with a greying chin and a few loose teeth; Nick was shocked to find that the canine was not a puppy at all but an old dog named Puppy. Under what rule did he cancel the agreement