In a double star, two stars of masses $m_1$ and $m_2$ distant r apart revolve about their common center of mass under their mutual gravitational attraction. Find the ratio of their kinetic energies $K_1 :K_2$

Question

$$(a)\;\frac{m_1r_1}{m_2r_2} \quad (b)\;\frac{m_1^2}{m_2^2} \quad (c)\;\frac{m_2^2r_1}{m_1^2r_2} \quad (d)\;\frac{m_2}{m_1}$$