[填空题]
An automobile engine s+) mys3 +6d-v ,a8etg+hsb pwmmi (ukqlows dohvf-lv38t gx9- t imf/wn 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. $rev$