The mass of a H- atom is less than the sum of the mass of a proton and electron , why is this ?

Question

$\begin{array}{1 1} \text{Mass of a H-atom }= m_p+m_e+B/c^2 \\\text{Mass of a H-atom }= m_p-m_e-B/c^2 \\ \text{Mass of a H-atom }= m_p-m_e+B/c^2 \\ \text{Mass of a H-atom }= m_p+m_e-B/c^2 \end{array} $