[填空题]
An automobile engine slpzi43l /,x zxgows down fr7l.f:c)*ol2xt kfv6 p4) 9lqujjvj 2gsyomf )om 4500 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. $rev$