Explanation:

Cost of goods sold              = Rs.60,000                         (3/5 of 1,00,000)

Selling Price of goods sold = Rs.70,000

Ordinary Commission         = Rs.1,400                        (2% on Rs.70,000)

Now, Let the extra commission be Rs.X

X=  20%[(70,000-1,400- X) - 60,000]  

x= 1/5 ( 68,600 - X - 60,000)

or, X= 1/5 ?*(8,600−X)

or, 5X=8,600−X

or, 6X = 8600

or, X=8,600?/6=1,433

Therefore, Total Commission = Rs.(1,400+1,433) =Rs.2,833