$4-$A wheel of rotational inertia, $I=4kg-m^2$ about its fixed central axis has an initial angular

velocity, $w_i=9ra\frac{d}{s}$ at $t=0.$ Its angular acceleration is$,=3ra\frac{d}{s^2}.$ Find: $($a$)$ the angular

velocity of the wheel at $t=2s.$ What is the angular displacement $()$ of the wheel during the

$2s.($b$)$ Find the net torque acting on the wheel. What is time rate of change of the angular

momentum?