Use Kepler’s first law to derive explicit expressions for the perihelion and aphelion distances for a planet in terms of the semi-major axis a, and the eccentricity e, for an elliptical orbit. Calculate these distances for Mercury.
(b)  What are the perihelion and aphelion speeds of Mercury?
(c)  Calculate the maximum angular separation of Mercury as seen from Earth. (d)  What is the angular size of Mercury in arcseconds when it is at this location?