[填空题]
An automobile engine slows down fromt1xedt) d xy*f;gm4bs; - ivu7 4500 rpm to 1200 rpm in 2.5 s. Calcul5*q bj+q tifx-ate (a) its angular acceleration, assumed constant, $rad/s^2$ (b) the total number of revolutions the engine makes in this time. $rev$