[填空题]
An automobile engine slows dt-o;g apv8r0down from 4 jmm 3x4s jb9y r5-,ukam/q3;z;vkl pg500 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. $rev$