You hold a brick at the surface of the Earth and lift it up by 1m at a constant, negligible speed. You repeat this experiment with the same bring at 10,000 km above the Earth's surface. The amount of work you do is...

a. the greatest near the surface and the lowest at 10,000 km above the surface because the force you exert to lift the brick gets smaller as you move farther from Earth while the distance the brick is moved stays the same

b. the lowest near the surface and the greatest at 10,000 km above the surface because the force you exert to lift the brick gets larger as you move farther from Earth while the distance the brick is moved stays the same

c. equal in both places because both the force you exert to lift the brick and the distance the brick is lifted are the same at both heights

d. the lowest near the surface and the greatest at 10,000 km above the surface because there is more gravitational energy in the {brick; Earth} system when the brick is farther from the surface of Earth