[填空题]
An automobile engine slows down from ph527agz jx55 2umcuaa ektu;h*el:,4500 rpm to 1200 rpm r zmnyyj .9k63mx,s*l 7a5lbnin 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. $rev$