Energy of hydrogen atom at ground state is $-13.6 \mathrm{eV}$.

The relation between the principle quantum number and the energy is given by,

$$\begin{gathered} E=\frac{-13.6}{n^2} \\ \Rightarrow E=\frac{-13.6}{16}=-0.85 \mathrm{eV} \end{gathered}$$

Potential energy of an electron in an orbit is twice that of the total energy. Therefore,

$PE=-1.7 \mathrm{eV}$