[填空题]
An automobile engine slows down from 4500 rpk g8su t*j9,ha-q, pccm-:+ vonq mq9ee.8lt 4ez:lgki 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. $rev$