[填空题]
An automobile engine slow9vgy: e:n1hwox*v9g w s down from 4500 rpm to 1200kkdyt;/h;q7*f 5g vlb 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. $rev$