Answer:
1000s
Step-by-step explanation:
Let t1 be time for 2km in 3m/s
t1= 2000/3
And t2 in the next 2km
t2= 2000/v.
So finding the average velocity
4000/t1+t2
=4000/2000(1/3+ 1/v)
V= 6m/s..
For 9km distance in 6m/s
The whole trip is 4m/s
So total time
4000/4=1000s