The angle of elevation of a jet plane from a point A on the ground is 60°. After a flight of 20 seconds at the speed of 432 km/hour, the angle of elevation changes to 30°. If the jet plane is flying at a constant height, then its height is :
1
\(3600\sqrt 3 \) m
2
\(2400\sqrt 3 \) m
3
\(1800\sqrt 3 \) m
4
\(1200\sqrt 3 \) m