A comet is moving in its orbit toward the Sun. As it approaches the Sun, part of the
comet evaporates from the Sun's heat. The comet and Sun exert a gravitational
force, F, on each other. After six weeks, the comet and Sun are one-fourth of their
original distance apart, and the comet is one-half of its original mass. Which of the
following is the force on the comet at this distance and mass?

2F

4F

8F

16F