[填空题]
An automobile engine slogdrmi3w)u 8 5h8.zhy yws down f0ci8,j )lv3z-v p( edupol.igrom 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. $rev$