Perpetual Inventory Using LIFO Beginning inventory, purchases, and sales data for prepaid cell phones for May are as follows: Inventory Purchases Sales May 1 1,400 units at $21 May 10 700 units at $23 May 12 980 units May 20 630 units at $25 May 14 840 units May 31 420 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. Schedule of Cost of Merchandise Sold LIFO Method Prepaid Cell Phones Quantity Cost of Merchandise Cost of Merchandise Sold Unit Cost Sold Total Cost Quantity Purchased Date May Purchases Unit Cost Purchases Inventory Quantity Inventory Unit Cost Inventory Total Cost May 12" May May Balances 31