A solid body rotates about a stationary axis so that the rotation angle `theta` varies with time as `theta=6t-2t^(3)` radian. Find
(a) the angular acceleration at the moment when the body stops and
(b) the average value of angular velocity and angular acceleration averaged over the time interval between `t=0` and the complete stop.
A. `6rad//s^(2)`
B. `24rad//s^(2)`
C. `18rad//s^(2)`
D. `12rad//s^(2)`
