A disk rotates about the central axis beginning from rest and accelerates with the constant angular acceleration. At one time it is rotating at 12 rad/s; 30 radians later, its angular speed is 25 rad/s. Compute (i) the angular acceleration (rad/s2), (ii) the time needed to complete the 30 radians, (iii) the time needed to arrive at the 12 rad/s angular speed, and (iv) the number of radians from rest till the time the disk arrives at the 12 rad/s angular speed.