[填空题]
An automobile engine slows down from 4500 rpm to 1200 r6mgvc * pkx;n6pm in 2.i/ oapm*ed3d//r v.tk23 mk(n f 3quxc5 s. Calculate (a) its angular acceleration, assumed constant, $rad/s^2$ (b) the total number of revolutions the engine makes in this time. $rev$