Left pan of a faulty balance weighs 100 gram more than its right pan. A shopkeeper keeps the weight measure in the left pan while buying goods but keeps it in the right pan while selling his goods. He uses only 1 kg weight measure. If he sells his goods at the listed cost price, what is his gain?

1. (a)200 1/11 %
2. (b)100/11 %
3. (c)100/9 %
4. (d)200/9 %