Can you also explain how you find these?

Perpetual Inventory Using LIFO The following units of a particular item were available for sale during the calendar year: Jan. 1 Inventory 3,900 units at $40 Apr. 19 2,300 units June 30 4.400 units at $45 Sept. 2 4,800 units Nov. 15 1,900 units at $48 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. Date Jan. 1 Apr. 19 June 30 Sept. 2 Nov. 15 Dec. 31 Sale Purchase Sale Purchase Quantity Balances 4,400 1,900 Purchases Unit Cost 45 48 Total Cost 198,000 91,200 Schedule of Cost of Goods Sold LIFO Method Quantity 2,300 Cost of Goods Sold Unit Cost $ 40 45 40 Total Cost $ 92,000 Quantity 3,900 1,600 1,600 4,400 1,200 1,200 1,900 Inventory Unit Cost $ 40 40 40 45 40 40 48 Total Cost $ 156,000 64,000 64,000 198,000 48,000 48,000 91,200 $ 139,200