posted by Joe .
new planet is discovered orbiting a distant star. Observations have confirmed that the planet has a circular orbit with a radius of 21 AU and takes 118 days to orbit the star. Determine the mass of the star. State your answer with appropriate mks units. [NOTE: AU stands for "astronomical unit". It is the average distance between Earth & the Sun. 1 AU ≈ 1.496 × 1011 m.]
I would use Keplers Law here.