Imagine a light planet revolving around a massive star in a circular orbit of raidus r with a a period of revolution T. If the gravitational force of attraction between planet and the star is proportioanl to `r^(-5)//^(2)`, then find the relation between T and r.
A. `R^(3//2)`
B. `R^(3//5)`
C. `R^(7//2)`
D. `R^(1//4)`
