[填空题]
An automobile engine 9xo a6rzyvdl c*8a/3q(e4yut slows down from 4500 rpo(f v b,do33fa8ak+cfeut3i) m 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. $rev$