A planet of mass M and radius R rotates so quickly that material at its equator only just remains on its surface. What is the period of rotation of the

planet? 2 \pi \sqrt{\frac{R^{3}}{G M}} 2 \pi \sqrt{\frac{G M}{R}} 2 \pi \sqrt{\frac{R}{G M}} 2 \pi \sqrt{\frac{G M}{R^{3}}}