[填空题]
An automobile engine slow1kxa;u w:+0s(oerp5gsqg+bpz ( ( sluyn *3qiv+3lc5asz x:h s 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. $rev$