Compute the approximate acceleration of gravity for an object above the earth's surface, assigning accel_gravity with the result. The expression for the acceleration of gravity is: (G * M) / (d 2), where G is the gravitational constant 6.673 x 10-11, M is the mass of the earth 5.98 x 1024 (in kg), and d is the distance in meters from the Earth's center (stored in variable dist_center).