What is the energy of an electron in the stationary state corresponding to $n=2$?

Which of the following relations is applicable for any $H$-like species?

The minimum energy that must be possessed by photons in order to produce the photoelectric effect with platinum metal is $.... \times 10^{-19} \, J$
[Given: The threshold frequency of platinum is $1.3 \times 10^{15} \, s^{-1}$ and $h = 6.6 \times 10^{-34} \, J \, s$.]

Among the following,which transition in the hydrogen spectrum would have the same wavelength as the Balmer transition,$n=4$ to $n=2$ in the $He^{+}$ spectrum?

The energy of an electron in the first Bohr orbit of the hydrogen atom is $-13.6 \ eV$. Calculate the energy of an electron in the first Bohr orbit of $He^{+}$ in $eV$.

What is the approximate angular momentum (in $J \ s$) of an electron in a hydrogen atom in its ground state? $(h = 6.625 \times 10^{-34} \ J \ s)$