“…The optimal process time of machine on each product type should be the same in all planning periods as manager desires so, (7) because of preventive maintenance activities, the available time in each planning period could be different of the others, in other word, the makespan in each planning period should be less than or equal to available time of that period, (8) each product type has its own demand in every planning period that is a finite, deterministic and integer value, (9) there is no initial stock of inventory for each product type, (10) products should be produced in a way that there would be no lost sales until the end of the last planning period, but back order is allowed in every period except the last period. In the other words, the sum of the amounts produced and delivered to customer during all periods should not be less than the sum of demands over all of periods, (11) unit shortage cost and unit inventory holding cost are deterministic values that could be different from a period to another period, (12) setup consists of some activities for each product type such as adjusting the machine speed, changing the tool, brushing and cleaning the machine, etc. And cost of changing the setup is so high.…”