Beginning inventory, purchases, and sales data for prepaid cell phones for December are as follows:

Inventory Purchases Sales
Dec. 1 4,000 units at $30 Dec. 10 2,000 units at $32 Dec. 12 2,800 units
Dec. 20 1,800 units at $34 Dec. 14 2,400 units
Dec. 31 1,200 units

Assuming that the perpetual inventory system is used, costing by the LIFO method, determine the cost of goods sold for each sale and the inventory balance after each sale. Under LIFO, if units are in inventory at two different costs, enter the units with the HIGHER unit cost first in the Cost of Goods Sold Unit Cost column and LOWER unit cost first in the Inventory Unit Cost column.