[填空题]
A horse canters away from its trainer in a straight line, moving 1 s- )fyd,4+;2 tgwm6vzmyajr h50 m awak7nyh xy./x4* irv u5 akg)-hfixhf( 4y in 24.0 s. It then turns abruptly and gallops half*k f4vhx u7 a.i)-hxy5g 4 /rnhxkiyf(way 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.
