A motor drives a disk initially at rest through 23.9 rotations in \(5.0 \mathrm{~s}\). Assume the vector sum of the torques caused by the force exerted by the motor and the force of friction is constant. The rotational inertia of the disk is \(4.0 \mathrm{~kg} \cdot \mathrm{m}^{2}\). When the motor is switched off, the disk comes to rest in \(12 \mathrm{~s}\).

(a) What is the torque created by the force of friction?

(b) What is the torque caused by the force exerted by the motor?