A diatomic molecule is made of two masses $m_{1}$ and $m_{2}$ which are separated by a distance $r$. If we calculate its rotational energy by applying Bohr's rule of angular momentum quantization, its energy will be given by ($n$ is an integer)\\
(1) $\dfrac{(m_{1}+m_{2})^{2}n^{2}h^{2}}{2m_{1}^{2}m_{2}^{2}r^{2}}$\\
(2) $\dfrac{n^{2}h^{2}}{2(m_{1}+m_{2})r^{2}}$\\
(3) $\dfrac{2n^{2}h^{2}}{(m_{1}+m_{2})r^{2}}$\\
(4) $\dfrac{(m_{1}+m_{2})n^{2}h^{2}}{2m_{1}m_{2}r^{2}}$