A satellite with a mass = 8 1023 kg orbits around a planet which has a mass of = 6 1024 kg. The distance (centre to centre) between the planet and the moon is = 380,000 km.

a) What is the period of the orbit in days?

b) What is the gravitational potential energy of the system?

c) Show by explicit calculation of the sum of the kinetic energies of the moon and of the planet that the total kinetic energy is in fact - of the gravitational potential energy.