Last month Silver Star used a total of 4,000 hours of labor. Its labor relations policy will not allow the combined total hours of labor (Manufacturing plus assembly) to increase or decrease by more than 500 hours from month to month. In addition, the company charges monthly inventory at the rate of 2 % of the production cost based on the inventory levels at the end of the month. Silver Star would like to have at least 25 units of each model in inventory at the end of two months.