A space craft with a mass equal to .25*(mass of moon) is in orbit about the sun with a period of 3 years. a) calculate the average radius of the space craft's orbit. (the distance from the space craft to the sun). b) if this craft approached the earth so that it was one earth radius from the surface of the earth, what force would the space craft exert on you if your mass is 80kg? also, what force would the space craft exert on the earth itself?