[填空题]
An automobile engine slows dowg;pdm)+i. 6g xpi*nfmn from 4500 rpm to 1200 rpm s*d32xyb;dc b9ok e 8yin 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. $rev$