Two celestial bodies of masses \(m_{1}\) and \(m_{2}\) are orbiting their center of mass at a center-to-center distance of \(d\). Assume each body travels in a circular orbit about the center of mass of the system, and derive the general Newtonian form of Kepler's third law: \(T^{2}=4 \pi^{2} d^{3} / G\left(m_{1}+m_{2}\right)\).