[填空题]
An automobile enginei d44qbba.+ bhsqp1 i* sloki)me6n;hos8oed * 4jws down from 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. $rev$