Answer:
FIFO : Ending Inventory = $6,000, Cost of Goods Sold = $36,000
LIFO : Ending Inventory = $36,000, Cost of Goods Sold = $28,000
Weighted Average Cost Method : Ending Inventory = $10,500, Cost of Goods Sold = $31,500
Explanation:
FIFO
Assumes that the first goods received by business will be the first ones to be delivered to the final customer.
Ending Inventory
Ending Inventory = Units left × Earliest Price
               = 3000 units × $2
               = $6,000
Cost of goods sold
Cost of goods sold : 2000 units × $5 =  $10,000
                 6000 units × $4 = $24,000
                 1000 units  × $2 =  $2,000
                 Total           =  $36,000
LIFO
Assumes that the last goods purchased are the first ones to be issued to the final customer.
Ending Inventory
Ending Inventory    2000 units × $5 =  $10,000
                 6000 units × $4 = $24,000
                 1000 units  × $2 =  $2,000
                 Total           =  $36,000
Cost of goods sold
Cost of goods sold : 4000 units × $2 =  $8,000
                 5000 units × $4 = $20,000
                 Total          =  $28,000
Weighted Average Cost Method
The average cost of goods held is recalculated each time a new delivery of goods is received Issues are then priced out at this weighted average cost.
First Calculate the Average Cost
Average Cost = Total Cost / Total Units
            = (2000 × $5 + 6000 × $4 + 4000 × $2) / 12,000
            = $42,000 / 12,000
            = $3.50
Ending Inventory
Ending Inventory = Units left × Average Price
               = 3000 units × $3.50
               = $10,500
Cost of goods sold
Ending Inventory = Units Sold × Average Price
               = 9,000 units × $3.50
               = $31,500
