    Sentence 1: That is, as the discount is increased in  steps, the cost to the Postal Service of sorting the  mail that becomes workshared on step 4 is  probably greater than the cost of sorting the mail  that becomes workshared on step 3. This  assumption will be relaxed in Part Ill below, where  larger discount changes areconsidered.    Sentence 2: Part ill will further raise concerns  about the assumption.