An asteroid is moving along a straight line. A force acts along the displacement of the asteroid and slows it down. The asteroid has a mass of $4.5 \times 10^{4} \mathrm{kg},$ and the force causes its speed to change from 7100 to $5500 \mathrm{m} / \mathrm{s}$
(a) What is the work done by the force? (b) If the asteroid slows down over a distance of $1.8 \times 10^{6} \mathrm{m},$ determine the magnitude of the force.