A pulley of radius 2m is rotated about its axis by a force F = (20t – 5t2) newton (where t is measured in seconds) applied tangentially. If the moment of inertia of the pulley about its axis of rotation is 10kgm2, the number of rotations made by the pulley before its direction of motion if reversed, is
(a) less than 3
(b) more than 3 but less than 6
(c) more than 6 but less than 9
(d) more than 9
