An intelligent shopkeeper uses a special weighing balance in which one pan is heavier than the other. While purchasing the material, he places a 1 kg weight on the heavier side but while selling the same product, he places 1 kg weight on the lighter side. If he decides to sell his goods at the cost price and gets an overall gain of 50 %, then find the value by which one side of the balance is heavier than the other?

A. 100 gm
B. 150 gm
C. 200 gm
D. 250 gm
E. 300 gm