At absolute zero, all of the free electrons in the metal have energies less than or equal to the Fermi energy, so N(EF)=Ntotal. Using this equality, you can solve for the Fermi energy EF and find EF=32/3?4/3?22m(NtotalV)2/3. The term Ntotal/V is called the free-electron density and is usually denoted n. (Be sure not to confuse this number with the function n(E).) The free-electron density for gold is 5.90