Answer:
                              FIFO            LIFO              Weighted Average
Inventory cost =  $167,700      $145,600     $157,800
Explanation:
a) Data and Calculations:
Jan. 1       Inventory     1,000 units at $120  $120,000     $120,000
Feb. 17    Purchases    1,375 units at $128     176,000      296,000
July 21    Purchases    1,500 units at $136    204,000      500,000
Nov. 23  Purchases     1,125 units at $140     157,500      657,500
Dec. 31   Total units   5,000                        $657,500
Dec. 31   Inventory      1,200
Dec. 31   Units sold    3,800
Inventory cost by:
FIFO ( first-in, first-out method)
July 21    Purchases         75 units at $136  $10,200
Nov. 23  Purchases     1,125 units at $140   157,500
Dec. 31   Inventory      1,200                       $167,700
LIFO (last-in, first-out method)
Jan. 1       Inventory     1,000 units at $120   $120,000
Feb. 17    Purchases      200 units at $128      25,600
Dec. 31   Inventory      1,200                        $145,600
Weighted-Average Cost Method
Total cost of goods available/Total units available  for sale 
= $657,500/5,000
= $131.50 per unit
Inventory cost = $157,800 ($131.50 * 1,200)