Answer:
a. $4,790.
Explanation:
For LIFO we decrease from each month purchase the sales for the month as we sale the newest units first.
January: 15 units at $160 Â 8 units
15 - 8 = 7 units left
February: 25 units at $165 10 units
25 - 10 = 15 units left
May: 20 units at $170 14 units
20 - 14 = 6 units left
September: 17 units at $175 13 units
17 - 13 = 4 units
November: 15 units at $180 18 units
15 - 18 = Â -3 units
As we more than we purchase we take units from the previous month:
September 4 units - 3 = 1 left
Ending Inventory
7 units  at  $ 160  =  1,120
15 units at  $ 165  =  2,475
6 units  at $  170  =  1,020
1  units  at $ 175  =    175
total              4,790