[填空题]
An automobile engine cm15cl8drqfcw d *15p slows do 2m;c(wy +tnu/ aobdklf ;/+pon+9tvj 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. $rev$