In a close-packed lattice,how does the size of an octahedral void compare to that of a tetrahedral void?

If the number of atoms in a unit cell is $2$,then the number of tetrahedral and octahedral voids will be ....... and ....... respectively.

$A$ compound forms a hexagonal close-packed $(HCP)$ structure. What is the total number of voids in $0.5 \ mol$ of it? How many of these are tetrahedral voids?

$A$ compound is formed by two elements $M$ and $N$. Element $N$ forms a hexagonal closed pack $(HCP)$ array with $2/3$ of the octahedral holes occupied by $M$. The formula of the compound is $....$

When sodium is heated above $1000 \ K$,its crystal structure changes from $bcc$ to $fcc$. Assuming the metallic radius of the atom remains unchanged,the ratio of the fraction of volume occupied by atoms in $bcc$ and $fcc$ structures will be .......

$A$ compound is formed by two elements $A$ and $B$. Atoms of the element $B$ (as anion) make $ccp$ lattice and those of element $A$ (as cation) occupy all tetrahedral voids. The formula of the compound is