Ellipse Application Problem

The space shuttle travels in an elliptical orbit about the earth. The shuttle orbits such that it reaches a maximum 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 elipse. 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 is 8000 miles. Write and equation for the shuttle's orbit.

**So far I know that the equation for an ellipse is **$\displaystyle \frac {(x-h)^2}{a^2} + \frac {(y-k)^2}{b^2} = 1$.

**I'm kinda confused on information given in the problem. I don't know how it is applied to the equation of an ellipse.**