If Northern Optica manufactures part 4S that is used in one of its products. The unit product cost of this part is: Direct materials $ 18 Direct labor 10 Variable overhead 2 Depreciation of special equip. 6 Supervisor's salary. Avoidable General factory overhead Allocated 20 Unit product cost 560 Also assume the following information The $60 unit product cost is based on 20,000 parts produced each year An outside supplier has offered to provide the 20 000 parts at a cost of $50 per part Required: select the correct answer Continue to make the part to save $320000 O Buying the part to save $8000. O Buying the part to save $20000 O