9) It costs $20 to make a single unit using regular production and $25 to make a single unit using overtime production. Total overtime production is limited to 50 units for the five-month period. The manufacturing plant has a regular production capacity of 300 units per month and no units in inventory at the start of the planning period. There is a $10 per unit charge for holding inventory at the end of each month and the ending inventory of the five-month planning period should be zero. Develop an objective function and constraints to solve this problem. Forecast 250 200 | Month August September October November December 300 400 500