Answer:
a) Cost of Goods Sold under each method of inventory:
 1) Average Cost:
Beginning Inventory  600 units   $1,800
Purchases: January 12, 580 units 2,900
Purchases: January 26, 180 units  1,260
Cost of goods available for sale, 1,360 units $5,960
Less ending Inventory, 440 units   $1,927.20
Cost of goods sold, 920 units     $4,032.80
a2) FIFO:
Beginning Inventory  600 units   $1,800
Purchases: January 12, 580 units 2,900
Purchases: January 26, 180 units  1,260
Cost of goods available for sale, 1,360 units $5,960
Less ending Inventory, 440 units   $2,560
Cost of goods sold, 920 units     $3,400
a3) LIFO
Beginning Inventory  600 units   $1,800
Purchases: January 12, 580 units 2,900
Purchases: January 26, 180 units  1,260
Cost of goods available for sale, 1,360 units $5,960
Less ending Inventory, 440 units   $1,320
Cost of goods sold, 920 units     $4,640
a4) Specific Identification:
Beginning Inventory  600 units   $1,800
Purchases: January 12, 580 units 2,900
Purchases: January 26, 180 units  1,260
Cost of goods available for sale, 1,360 units $5,960
Less ending Inventory, 440 units   $2,280
Cost of goods sold, 920 units     $3,680
B. Partial Income Statement under:
                                   Average cost   FIFO    LIFO     Specific Identification
Beginning Inventory      $1,800        $1,800    $1,800          $1,800
Purchases                        4,160          4,160       4,160            4,160
Cost of goods for sale $5,960       $5,960   $5,960        $5,960
Less ending Inventory    1,927.20    2,560       1,320          2,280
Cost of goods sold     $4,032.80  $3,400   $4,640       $3,680
Explanation:
a) The average cost per unit under Average Method = 
Average cost per unit =$4.38 (5,960/1,360)
Ending Inventory, 440 x $4.38 = $1,927.20
b) Ending Inventory under FIFO: 440 units
Cost of 180 units = $1,260
Cost of 260 units =  1,300 (260 x $5)
Total cost = $2,560
c) Ending Inventory under LIFO: 440 units
Cost of 440 units from beginning inventory = 440 x $3 = $1,320
d) Ending Inventory under Specific Identification: 440 units
Remaining opening inventory 140 units at $3 = $420
Remaining Jan 12, 120 units at $5 = $600
Remaining Jan 26, 180 units at $7 = $1,260
Total cost of ending inventory = $2,280
e) These are various inventory costing methods which present different results in their cost of goods sold and the ending inventory.