[填空题]
An automobile engine slows 5qmr o:ec8u7 o76nhr1e*8sv rrhni )ndo29,bj xb-ydq 5e0grom 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. $rev$