Answer:
Periodic system: FIFO ; COGS= $11400, closing inventory = $7700, gross profit=$14000. LIFO = closing stock= 6600, COGS=$12500, gross profit=12900.
perpetual system: FIFO ;COGS=11400, closing stock= $7700, gross profit= $11400. LIFO ; COGS=$12500, closing stock= $6600, gross profit = $12900
Reason for a higher gross profit in FIFO than LIFO is some of the stock ends up not being sold as they are maybe old, out-fashioned, and obviously new trend come about everyday. 
Explanation:
 PERIODIC    
DR  purchases account    CR
11-Aug	bank	9600  inventory	16100
20-Aug	bank	6500    
      
                 <u>16100</u>                  <u> 16100
</u>
  FIFA cost of sales  
    
opening balance   3000
purchases     16100
closing             7700
cost of sales     <u> 11400</u>
gross profit  	<u>14000</u>
sales           25400
cost of sales  	11400
closing inventory           <u>7700</u>
200 units from 11 aug  	1200
1000 units from 20 aug  	6500
 LIFO  
 closing balance         <u>6600</u>
600 units from 01 aug  	3000
600 units from 11 aug  	3600
 Cost of sales  
opening stock  3000
purchases  	16100
closing stock  	6600
cost of sales  	<u>12500</u>
    
gross profit  	<u>12900</u>
sales         25400
cost of sales  	12500
perpetual inventory system    
  	FIFA
cost of sales  	<u>11400</u>
10-Aug  	2000
15-Aug  	5800
27-Aug  	3600