Cost of goods sold = 3/5 * 1,00,000 = Rs. 60,000
Selling Price of goods sold = Rs. 70,000
Ordinary Commission = 2% on Rs. 70,000 = Rs. 1,400
Now, Let the extra commission be Rs. X
Therefore, According to Problem:
X = 20% [(70,000 - 1,400 - X) - 60,000]
or, X = 1/5 * (8,600 - X)
or, 5X = 8,600 - X
or, X = 8,600/6 = 1,433
Therefore, Total Commission = Rs. (1,400 + 1,433) = Rs. 2,833