What is the coordination number of a cation in an ionic compound if the type of hole occupied by the cation is octahedral?

What is the total number of atoms present in an $fcc$ unit cell?

The coordination number of $Na^{+}$ in $NaCl$ is

In a mixed oxide of two metals $X$ and $Y$,divalent $X^{2+}$ ions occupy $50\%$ of the tetrahedral voids,while trivalent $Y^{3+}$ ions occupy $50\%$ of the octahedral voids. The formula of the oxide is:

What is the mass of a $bcc$ type unit cell of sodium if the mass of one atom of sodium is $3.819 \times 10^{-23} \ g$?

In $NaCl$ type structure, the shortest distance between two nearest neighbours is $100 \ pm$. Then, the distance between two next nearest neighbours in the same unit cell will be: