The Tingey Company has 500 obsolete microcomputers that are carried in inventory at a total cost of $720,000. If these microcomputers are upgraded at a total cost of $100,000, they can be sold for a total of $160,000. As an alternative, the microcomputers can be sold in their present condition for $50,000. The sunk cost in this situation is: 1) $720,000. 2) $160,000. 3) $ 50,000. 4) $100,000. show work please