[填空题]
An automobile engine slows down from 4500 rpm to : plulkwy(xl0e:* r 3r 4zyrt*1200 rpm in 2.ta 4ha:ms8xbd;aczom 231 f-s7gn3ej5 s. Calculate (a) its angular acceleration, assumed constant, $rad/s^2$ (b) the total number of revolutions the engine makes in this time. $rev$