[SOLVED] Ellipse and Circle problem

Hey everybody!

I have this problem and my solution was:

(x-h)/40,000 + (y-k)/10,000 = 1

Here's the problem:

The space shuttle travels in an elliptical orbit about the earth. The shuttle orbits such that it reaches a max height above the surface of the earth of 200 miles and a minimum height above the surface of 100 miles. The center of the earth is one focus of the ellipse. Assume that the center of the ellipse is at the origin and the major axis is horizontal. also assume the earth is circular. The approximate diameter of the earth 8000 miles. Write an equation for the shuttle's orbit.

The equation up there is what I got. I just seem a bit hesitant because it seemed really easy. Is it correct?

Thanks,

Stealth