Above the surface of the Earth, the magnitude of the acceleration due to gravity is inversely proportional to the square of the distance from the Earth's center. For objects falling to Earth, a = k/r2, where k is a constant and r is the distance to the center of the Earth. (a) The radius of the Earth is about 6.40×103 km. Find k using the fact that a = g at Earth's surface. (b) Find the magnitude of the acceleration due to Earth's gravity at 1.00×102 km above the surface of the Earth.