A disk rotates about its central axis starting from rest and accelerates with constant angular acceleration. At one time it is rotating at 4.1 rad/s; 45 radians later, its angular speed is 16 rad/s. Calculate (a) the angular acceleration (rad/s2), (b) the time required to complete the 45 radians, (c) the time required to reach the 4.1 rad/s angular speed, and (d) the number of radians from rest until the time the disk reaches the 4.1 rad/s angular speed.