[填空题]
An automobile engine slows dowusv u,w: fi.6jac;db( n fp o;wckcvc2lcr .3cr-r x0: 5krom 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. $rev$