Answer:
404.98 m
Step-by-step explanation:
The angle of depression is 5°
The horizontal distance from the airplane to the atoll is 4629 meters.
We need to find the height of the plane.
If we consider a triangle. 4629 meters will be the base and angle is 5°. Let h is the height of the plane. Using trigonometry to find it :

So, the height of the plane is 404.98 m.
If you meant:
64.3-3*(2³)/2
That would be 52.3 :)