9. An asteroid has a perihelion distance of 2.0 AU and aphelion distance of 4.0 AU. Calculate its orbital period. [Hint: you must find the semi-major axis using equation 1 and then use Kepler's 3" Law (equation 2) to find the period.] 10. Calculate the mass of star Vulcan given that a planet is in a circular orbit around it at a distance, a, of 2 AU with an orbital period of 3 years. (Hint: Use equation 3.)