A large disc has mass 2 kg and radius 0.2 m and initial angular velocity 50rad/s and a small disc has mass 4kg and radius 0.1m and initial angular velocity 200 rad/s, both rotating about their common axis. Then the common final angular velocity after discs are in contact is,

Options

A. `100 rad//s`
B. `125 rad//s`
C. `200 rad//s`
D. `150 rad//s`