i need explanation pleaseeee

Sale The following units of an item were available for sale during the year: Beginning inventory 21,600 units at $20.00 Sale 14,400 units at $40.00 First purchase 48,000 units at $25.20 Sale 36,000 units at $40.00 Second purchase 45,000 units at $26.40 33,000 units at $40.00 Use Table perpetual inventory system FIFO and LIFO to calculate: Cost of inventory sold Inventory balance at the end of the period Calculate gross profit under the both system