[填空题]
An automobile engine slows down from 45n6 .corl,c vx 1-(aa wxbhaj4900 rpmc jh+u/7 t(veu k+y+qx 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. $rev$