Two stars of masses m and 2m at a distance d rotate about their common centre of mass in free space. The period of revolution is
1
\(2 \pi\sqrt{\frac{d^3}{3 G m}}\)
2
\(\frac{1}{2 \pi}\sqrt{\frac{3 G m}{d^3}}\)
3
\(\frac{1}{2 \pi}\sqrt{\frac{d^3}{3 G m}}\)
4
\(2 \pi\sqrt{\frac{3 G m}{d^3}}\)