Stein, a mechanic, and Beal, a life insurance agent, entered into a written contract for the sale of Stein's tractor to Beal for $6,800 cash. It was agreed that Stein would tune the motor on the tractor. Stein fulfilled this obligation and on the night of July 1 telephoned Beal that the tractor was ready to be picked up upon Beal's making payment. Beal responded, ‘‘I'll be there in the morning with the money.'' On the next morning, however, Beal was approached by an insurance prospect and decided to get the tractor at a later date. On the night of July 2, the tractor was destroyed by fire of unknown origin. Neither Stein nor Beal had any fire insurance. Who must bear the loss?