The Mars orbits Sun at a mean orbital radius of 228 Gm (1 GM = 10^9 m) and consists of an orbital period of 687 d. Earth orbits the Sun at a mean orbital radius of 149.6 Gm.
(i) The Earth-Sun line sweeps out an angle of 360° throughout one Earth-year. Around what angle is swept out by the Mars-Sun line throughout one Earth-year?
(ii) Determine how frequently are Mars and the Sun in opposition (on diametrically opposite sides of the Earth)?