What is the coordination number of a cation occupying an octahedral void?

Explain the calculation of the number of atoms in a primitive cubic unit cell.

The intermetallic compound $LiAg$ crystallizes in a cubic lattice in which both lithium and silver have a coordination number of $8$. The crystal class is

The compound $AB$ crystallizes in a cubic lattice in which both $A$ and $B$ atoms have coordination numbers of $8$. To what crystal class does the unit cell belong?

The unit cell of a $NaCl$ lattice:

What is the percentage of void space in $bcc$ type of unit cell (in $\%$)?