At room temperature, the electrical conductivity and electron mobility for aluminium are $3.8 \times 10^{7}(\Omega \mathrm{m})^{-1}$ and $0.0012 \mathrm{~m}^{2}(\mathrm{~V} \mathrm{~s})^{-1}$, respectively. Density of free electrons for aluminium at room temperature is $\text{(in units of $\mathrm{m}^{-3}$ )}$ __________ $\times 10^{27}$ $\text{(rounded off to nearest integer)}$.
Given: Electrical charge on an electron is $1.6 \times 10^{-19} \mathrm{C}$.
