FIFO means First Come First Out.
In FIFO Method the Inventory Comes First are deducted from Inventory First at the time of Sales or transfer to Production unit. Based on this methodology the Value of Closing Stock will be :
Value of Closing Inventory = $ 3400.00
Value of Cost Sold = $7,600 + $7,200 + $3120 + $3400
Total = $ 21,400
cost of goods sold is $ 21,400