Perpetual Inventory Using FIFO Beginning inventory, purchases, and sales for Item Zeta9 are as follows: Assuming a perpetual inventory system and using the first-in, first-out (FIFO) method, determine (a) the cost of goods sold on October 24 and (b) the inventory on October 31. Feedback Fereck My Werk a. When the FIFO method is used, costs are included in cost of goods sold in the order in which they were purchased. Think of your inventory in terms of "layers". Determine how much inventory re b. The ending inventory is made up of the most recent purchases