Perpetual Inventory Using LIFO Beginning inventory, purchases, and sales data for prepaid cell phones for May are as follows: Inventory Purchases Sales May 1 3,700 units at $38 May 10 1,850 units at $40 May 12 2,590 units May 20 1,665 units at $42 May 14 2,220 units May 31 1,110 units a. Assuming that the perpetual inventory system is used, costing by the LIFO method, determine the cost of merchandise sold for each sale and the inventory balance after each sale, presenting the data in the form illustrated in Exhibit 4. Under LIFO, if units are in inventory at two different costs, enter the units with the HIGHER unit cost first in the Cost of Merchandise Sold Unit Cost column and LOWER unit cost first in the Inventory Unit Cost column.