I need help understanding how to get LIFO units of 2000 and 2400 in the solutions problem. i don't understand how they got those units to solve the problem. Please show work.

Riverbed Corp. had 2,000 units of part T on hand April 1, 2017, costing $8.00 each. During April, Riverbed made the following purchases of part T. Unit Cost Units April 4 2,800 $8.25 10 4,900 8.40 19 1,100 9.00 29 3,000 9.90 A physical count at April 30, 2017 showed 4,400 units of Part T on hand. Using the FIFO method, what is the cost of part Tinventory at April 30, 2017? Using the LIFO method, what is the inventory cost? Using the average-cost method, what is the inventory cost? (Round average cost per unit to 2 decimal places, e.g. 15.25 and final answers to O decimal places, e.g. 1,620.) LIFO inventory cost: 2,000 units at $8.00 $16,000 2,400 units at 8.25 19,800 Total $35,800