Which from following combinations is an example for construction of n-type semiconductor?

Calculate the density of metal having molar mass $$210 \mathrm{~g} \mathrm{~mol}^{-1}$$ that forms simple cubic unit cell. $$\left(\mathrm{a}^3 \cdot \mathrm{N}_{\mathrm{A}}=21.5 \mathrm{~cm}^3 \mathrm{~mol}^{-1}\right)$$

Calculate the volume of unit cell if an element having molar mass $$56 \mathrm{~g} \mathrm{~mol}^{-1}$$ that forms bcc unit cells.

$$\left[\rho \cdot \mathrm{N}_{\mathrm{A}}=4.8 \times 10^{24} \mathrm{~g} \mathrm{~cm}^{-3} \mathrm{~mol}^{-1}\right]$$

In an ionic crystalline solid, atoms of element Y forms hcp structure. The atoms of element X occupy one third of tetrahedral voids. What is the formula of compound?