8. Refer to the data in Problem 6. If backorders are allowed, determine the total cost of a plan if overtime is limited to 40 units per month and subcontracting is limited to 20 units per month. Backordering costs are $30 per unit. 6. Given the following forecast and cost information, determine the total cost of a plan that uses regular time production output of 600 units per month, overtime is used when needed up to a maximum of 60 units per month, and subcontracting is used if additional units are needed to meet the forecast. our operations 2 Month 3 4 5 6 570 600 630 Forecast 650 670 690 Regular time cost = $40 per unit Overtime cost = $60 per unit Subcontracting cost = $80 per unit Holding cost = $10 per unit per month Note: Holding costs for each month are calculated on the average inventory level and in U.S. dollars