[填空题]
An automobile engine slows down from 4500 ifg d/2mxrm+0 rpm to 1200ibf- 9 le)3rs9jow0i; 7gicnv 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. $rev$