[填空题]
An automobile engine sw5jy8w uv3eg(r9 hhix *lm8ghsc -4:rlom4 f-e bb2tgnd(lk,1iws down from 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. $rev$