[填空题]
An automobile engine lc9v 4cjh4ovpn4 w, n9slows down from 4500 rpm to j/uyh4)fcpt/mc dr 7(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. $rev$