Communications satellites are typically placed in orbits of radius \(r_{C S}\) circling the earth once per day. The 24 or so GPS (Global Positioning System) satellites are placed in one of six orbital planes, with each satellite circling the earth twice per day.

(a) Find the radius of their orbits as a fraction of \(r_{C S}\).

(b) Low-earth orbit satellites typically have orbital periods of about 90 minutes. Find their radii as a fraction of \(r_{C S}\).