What is the total number of Bravais lattices present for different crystal systems?

Calculate the molar mass of an element with density $$2.7 \mathrm{~g} \mathrm{~cm}^{-3}$$ that forms fcc structure. $$\left[\mathrm{a}^3 \cdot \mathrm{N}_{\mathrm{A}}=40 \mathrm{~cm}^3 \mathrm{~mol}^{-1}\right]$$

Identify the CORRECT decreasing order of melting point of cluster of sodium atoms depending on size.

Calculate the molar mass of an element having density $$21 \mathrm{~g} \mathrm{~cm}^{-3}$$ that forms fcc unit cell $$\left[\mathrm{a}^3 \cdot \mathrm{N}_{\mathrm{A}}=36 \mathrm{~cm}^3 \mathrm{~mol}^{-1}\right]$$