[填空题]
A horse canters away fry;*0 i bnb*dvt 2ozor1om its trainer in a straight line, moving 150 m away in t-9z- :pipp uu24.0 s. It the9pi -ztpu -p:un turns abruptly and gallops halfway back in 7.5 s. Calculate (a) its average speed $m/s$ and (b) its average velocity $m/s$ for the entire trip, using “away from the trainer” as the positive direction.
