[填空题]
An automobile engine slows down frog g 0oo5c)6nnq t;.-vur ga:iom 4500 rpm ac inhtbh) s,1)z2 e3un qb4io.gzh(5to 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. $rev$