The Force of Gravity (Outside the Earth) Attracting a Mass

Multiple Choice

The force of gravity (outside the Earth) attracting a mass m is proportional to the mass m and inversely proportional to the square of the distance from the centre of the Earth. Find the work done in moving a mass that weighs 1 lb at the surface of the Earth to 10 miles above the surface. Assume the radius of the Earth is 4,000 mi. At the Earth's surface, a force of 1 lb is required to lift a mass of 1 lb.

A) 48,193 ft . lb
B) 50,327 ft . lb
C) 51,420 ft . lb
D) 52,668 ft . lb
E) none of the above