For each planet in a solar system, its year is the time it takes the planet to revolve around the center star. The function f (x )equals 0.2 x Superscript 3 divided by 2 models the number of Earth days in a planet's year, f(x), where x is the average distance of the planet from the center star, in millions of kilometers. There are approximately 365 Earth days in the year of Planet Upper C. What is the average distance of Planet Upper C from the center star?