The work function of the metal $\mathrm{A}$ is equal to the ionization energy of the hydrogen atom in the first excited state. The work function of the metal $\mathrm{B}$ is equal to the ionization energy of ${\mathrm{He}}^{+}$ion in the second orbit. Photons of the same energy $E$ are incident on both $\mathrm{A}$ and $\mathrm{B}$. The maximum kinetic energy of photoelectrons emitted from $\mathrm{A}$ is twice that of photoelectrons emitted from $\mathrm{B}$. Value of $E$ ( in $\mathrm{eV}$) is