Perpetual inventory using FIFO Beginning inventory, purchases, and sales data for DVD players are as follows: The business maintains a perpetual inventory system, costing by the first-in, first-out method. a. Determine the cost of goods sold for each sale and the inventory balance after each sale, presenting the data in the form illustrated in Exhibit 3. Under FIFO, if units are in inventory at two different costs, enter the units with the LOWER unit cost first in the Cost of Goods Sold Unit Cost column and in the Inventory Unit Cost column