[填空题]
An automobile engine slows 3txd3+ n3kkq u zz*9jm yjix,w1 p;t1rdown from 4500 9e:ffkwjq9rdo) a8e4eg, 2)8n c nrbh 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. $rev$