<span>θ is the angle whose tangent is 3/0.4 = arctan (7.5) = 82.4°
(That's the angle above the horizontal. If that doesn't match
the </span><span>θ in your diagram, too bad ! For some strange reason,
I wasn't able to see your diagram.)
</span>
There is no definite end to earths atmosphere, but technically the border between the outer space and earth gets thinner as you move up from the earths surface. The Karman line is the closest definition there is which describes the end of the earth's atmosphere, it is 100 km above earth's sea level at approximately 1.56 % of total earth's radius. This describes the boundary between the outer space and the atmosphere.
Speed of man towards West =2.5 m/s
Time to travel in the given direction = 1200 s
Total displacement towards west


Now speed of man towards East = 1 m/s
time to travel in east direction = 500 s
total displacement towards East


Now total displacement will be


so it is 2500 m towards west