Hume, who was not a merchant, agreed to sell his tractor to Warne for $1,500. Hume told Warne that it was available for him to pick up anytime. Warne paid for the tractor and said that he would pick it up the next day. A week later the tractor was stolen from Hume’s property. It had not been picked up by Warne as agreed. Must Warne or Hume suffer the loss? Why?