Perpetual inventory using lifo the following units of a particular item were available for sale during the calendar year: jan. 1 inventory 4,000 units at $39 apr. 19 sale 2,400 units june 30 purchase 4,500 units at $44 sept. 2 sale 5,000 units nov. 15 purchase 2,000 units at $46 the firm maintains a perpetual inventory system. determine the cost of goods sold for each sale and the inventory balance after each sale, assuming the last-in, first-out method. present the data in the form illustrated in exhibit 4. under lifo, if units are in inventory at two or more different costs, enter the units with the lower unit cost first in the inventory unit cost column.