Write a function describing the relationship of the given variables.


$\displaystyle {A}$ varies inversely with the cube of $\displaystyle {r}$ and when $\displaystyle {r}={3}$, $\displaystyle {A}={576}$. Find $\displaystyle {r}$ when $\displaystyle {A}={243}$


$\displaystyle {r}=$Preview Question 6