$(2$ pt$.)($a$)$How could you determine the distance from a planet to the star?

$(2$ pt$.)($b$)$How could you measure the diameter of the planet?

$(3$ pts$.)($c$)$How could you determine the mass of the planet?

$(2$ pt$.)($d$)$How could you determine the density of the planet?

$(1$ pt$.)($e$)$Why is it useful to know the mean density of a planet?