An employee, let's call him Keith, walks into the hub for his twilight shift and the sort manager, Tim, happens to be standing there. Tim tells Keith (who is the most senior employee on his PD) that he is going to be working in the unload tonight. Keith informs him that he has seniority and would prefer to remain on his PD. Tim says that if Keith doesn't immediately report to the unload he will be fired for failing to work as directed. Keith simply laughs and walks away. What did Keith find so funny?