Since Selenium is two columns to the right of Silicon, we know that it must be a n-type Extrinsic Semiconductor.

Each atom of Selenium donates two electrons. Therefore, the number of atoms per cubic meter must be multiplied by two to get the number of donated electrons.

$p = 2 \times 10^{20} \text{atomes}\;m^{-3},$

$\sigma = 2 \; p \; e \; \mu_h = $$ 2 \times 10^{20} \times e \times 0.14 =$$ 4.48\; (\Omega \; m)^{-1}$