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 . 4. Cost of goods sold on October 24 x b. Inventory on Octobee 31