An ice storm occurs in Metropolis on Monday. On Wednesday, with temperatures still below freezing, Arnold, a mailman, who is by custom is required to deliver mail in "rain, sleet, or snow" slips and falls on Carter's walkway while attempting to deliver Carter's mail. Arnold breaks his arm in the fall. Arnold sues Carter, alleging that Carter should have cleaned his walkway, and place salt on the walkway to remove the ice. Will Arnold prevail in his suit? Why or why not? What must Arnold show to win? What defenses are available to Carter?