XYZ Company makes a special type of wrench in one of its factories. The marketing department has estimated the demand of this product during the next six months to be as follows: With its current labour force, the Company believes it can make approx. 4 2 0 pipe wrenches per month at a cost of $ 4 0 per wrench using regular time production. An additional 8 0 wrenches per month can be made using overtime production, but then the cost per wrench is $ 4 5 . Wrenches can be made in one month and can be held in inventory for later shipment at a cost of $ 3 per month per wrench. Beginning inventory is 1 0 wrenches. The monthly demand for wrenches must be satisfied every month. Find out the production plan for above six months.