Mars orbits the Sun at a mean orbital radius of 228 Gm (1Gm=10^9m) and has an orbital period of 687 days. Earth orbits the Sun at a mean orbital radius of 149.6Gm (a) The Earth-Sun line sweeps out angle of 360degrees during one earth-year. Approximately what angle is swept out by the Mars-Sun line through one Earth-year? (b) How frequently are Mars and the Sun in opposition (on diametrically opposite sides of the Earth)?