a) Describe Kepler's three laws of planetary motion, using sketches to illustrate youranswers where appropriate. b) Starting from Newton's law of gravitation, derive a proof for Kepler's third law, givena circular orbit. c) The orbits of Earth and Uranus round the Sun may be considered as circular, withmean orbital radii of rE = 1.50 x 10¹1 m and ru = 2.87 x 10¹2 m respectively. If theperiods of orbit round the Sun are 365.3 days for the Earth and 30,705 days (or 84years) for Uranus: i.Show that these figures are approximately consistent with Kepler's thirdlaw. ii.Explain the possible reasons for any small discrepancies arising. iii.Estimate the mass of the Sun. iv.Hence, what is the difference in gravitational potential betv5/6wopoints with distances re and ry away from the Sun?