12) A satellite remains at the same position above the earth's surface at all times. At approximately what height above the surface must it be, assuming the orbit is circular? Hint: Use the period of the satellite's orbit and Kepler's third law of planetary motion. Use G = 6.67 x 10-11, and assume the mass of Earth is 5.98 x 1024 kg and its radius is 6.38 x 106 meters.