Calculate the interval (in eV units) between neighbouring levels of free electrons in a metal at \(T=0\) near the Fermi level, if the concentration of free electrons is \(n=2.0 \cdot 10^{22} \mathrm{~cm}^{-3}\) and the volume of the metal is \(V=1.0 \mathrm{~cm}^{3}\).