Answer:
At higher elevations, there are fewer air molecules above a given surface than a similar surface at lower levels. ... Since most of the atmosphere's molecules are held close to the earth's surface by the force of gravity, air pressure decreases rapidly at first, then more slowly at higher levels.
Explanation:
I DONT know FiGURE it out YOURSELF
Convert km to m. -> 320km=320000 m
Convert hours to seconds -> 4 hrs=14400 s
Divide the distance by time because v=d/t
320000/14400=22.22 m/s
