An object of mass 40.0 kg rests on the surface of a planet with a mass of 8.2 x 11.022 kg and radius 3.6 x 105m. a. Calculate the force of gravity acting on the object. b. Determine the gravitational field strength "g" at the planet's surface. c. Calculate the force of gravity acting on the object if it is placed at a position 6.4 x 105 m above the planet's surface