Suppose the gravitational force varies inversely as the $n^{th}$ power of distance, then the time period of planet in circular orbit of Radius 'R' around the sun will be proportional to

Question

$$(a)\;R^n \quad (b)\;R^{\bigg(\Large\frac{n-1}{2}\bigg)} \quad (c)\;R^{\bigg(\Large \frac{n+1}{2}\bigg)} \quad (d)\;R^{\bigg(\Large \frac{n-2}{2}\bigg)}$$