[填空题]
An automobile engine slows dy2o)38yw28 vubnfp 8y-xbjo3/bo mu down from 4500 rp-mijeg.407.phr7d t04 bga m/vmubl3t xf z,x m 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. $rev$