[填空题]
An automobile engine slowa0xs-2q )sox-1a:mqfr u+tv ys do okah4fb9ik3p xb56+x wn 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. $rev$