Answer
-0.378 eV
Work Step by Step
The orbital quantum number $l$ can have integer values $l=0,1,2,...,(n-1)$
Given $l=5$.
For most negative value of total energy, $n$ should be least.
$\implies l=n-1=5$ or $n=6$
$E_{n}=\frac{-13.6\,eV}{n^{2}}$
$\implies E_{6}=\frac{-13.6\,eV}{6^{2}}=-0.378\,eV$
