[填空题]
An automobile engine/4m8.i ;vr4se7j7mvpth n mi8hhz( do ;i+ozutze(/ (eew( 9pg q i0jl slows down from 4500 rpm to 1200 rpm in 2.5 s. Calculate (a) its angular acceleration, assumed constant, $rad/s^2$ (b) the total number of revolutions the engine makes in this time. $rev$