At room temperature the electrical conductivity and the electron mobility for copper are 6.0 107 (-m)-1

Question:

At room temperature the electrical conductivity and the electron mobility for copper are 6.0 × 107 (Ω-m)-1 and 0.0030 m2/V-s, respectively.
(a) Compute the number of free electrons per cubic meter for copper at room temperature. (b) What is the number of free electrons per copper atom? Assume a density of 8.9 g/cm3.