[填空题]
A horse canters away from its trainer in a straight line, moving 150 mflchx9d)ao.5i- g7s c 9w)2hmtr e)qq aw tmu):2pyo+3vvh2m+(kzkh e b+mz94o3f it tp ay in 24.0 s. It then turns abruptly and gallops halfway back in 7.5 s. Calculate (a) 3ov+yzkth tzv4m )2mukb3pep 29ot+hf:m(i +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.
