Answer:
Option e) 320 s
Explanation:
Here, distance = 3.0 km = 3000 m
The velocity of boat when it is going upstream;
Upstream velocity = velocity of boat in still water - velocity of river flow
So, Upstream velocity 
So,Time to go upstream

The velocity of boat when it is going downstream;
Downstream velocity = velocity of boat in still water + velocity of river flow
So, Downstream velocity 
So,Time to go downstream

So, total time (t) = 
Option E is the correct answer.
I don't get what you're trying to say, I only see A. and B. so I will say the answer is possibly A.
38*10=380 N
To be more exact, 38 should be multiplied by 9.8 instead of 10.
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The main function of the cardiovascular system is therefore to maintain blood flow to all parts of the body, to allow it to survive. Veins deliver used blood from the body back to the heart.