A cloth merchant buys cloth from a weaver and cheats him by using a scale which is 10 cm longer than a normal metre scale. He claims to sell cloth at the cost price to his customers, but while selling uses a scale which is 10 cm shorter than a normal metre scale. What is his gain?

Options

A. `20%`
B. `21%`
C. `22(2)/(9)%`
D. `23(1)/(3)%`