Answer: +17 m/s ==> option 4
Explanation:
4 km + 8 km + 8.9 km=
12+8.9=20.9 km
1 km=1000 m
20.9 km * 1000 m/1 km=
20.9 * 1000/1=
20.9 * 1000=20900 m
1 min = 60 sec
20 min * 60 sec/1 min=
20*60/1=
20*60=1200 minutes
20900/1200=
209/12=17.4
17.4=+17 m/s ==> option 4