Halley's Comet orbits the sun about every 75 years due to the gravitational force the sun provides. The distance between Halley's Comet and the sun when the comet is at aphelion (its greatest distance from the sun) is about 4.5 x 1012 m and the distance at perihelion (or closest approach) is about 5.0 x 1010 m. If the mass of the sun is 1.99 x 1030kg what is the comet's acceleration a) at aphelion? b) at perihelion?