A circular coil of radius 4 cm has 50 turns. In this coil a current of 2 A is flowing. It is placed in a magnetic field of `0.1 weber//m^(2).` The amount of work done in rotating it through `180^(@)` from its equilibrium position will be
A. `0.1J`
B. `0.2J`
C. `0.4J`
D. `0.8J`