[填空题]
An automobile engine slows down from 4500 rpm to ll5+8dc9polhvpn( 1 m ta/hd0 1200 rpt0nn:8x knd/jm 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. $rev$