An experiment using the Cavendish balance to measure the gravitational constant G found that a uniform O.40O-kg sphere attracts another uniform 0.00300-kg sphere with a force of 8.00 X 10- 10 N, when the distance between the centers of the spheres is 0.0100 m. The acceleration due to gravity at the earth's surface is 9.80 m/s and the radius of the earth is 6380 k/n. Compute the mass of the earth from these data.