4. AL ZAIN ltd uses a periodic inventory system. Its records show the following for the month of May, in which 46 units were sold Date Particulars Units Unit Cost Total Cost May 1 Inventory 359 315 17 Purchases 35 7 2 45 20 Purchases 10 12 120 Total 80 680 Instructions: Compute the ending inventory at May31st and the cost of goods sold using the FIFO, LIFO and the average-cost method