I would start of by deriving the energies; kinetic and total to be exact (which aren’t too difficult). Then you can derive Kepler’s third law by analysing and equating it with orbital velocity (might’ve to derive that as well)kepler's laws though? do we just disregard the first two and only talk about the third? i don't see the relevance of the question to the first two kepler's laws.
(i'd also appreciate it if you weren't so arrogant, thanks.)