Disk a has a mass of 6 kg and an initial angular velocity of 360 rpm clockwise; disk b has a mass of 3 kg and is initially at rest. the disks are brought together by applying a horizontal force of magnitude 20 n to the axle of disk a. knowing that µk = 0.15 between the disks and neglecting bearing friction, determine (a) the angular acceleration of each disk, (b) the final angular velocity of each disk.