How much part of an atom occupies each corner of a $bcc$ unit cell?

Element '$B$' forms $ccp$ structure and '$A$' occupies half of the octahedral voids,while oxygen atoms occupy all the tetrahedral voids. The structure of bimetallic oxide is

In a face-centered cubic $(FCC)$ unit cell (or cubic close packing $(CCP)$ unit cell),the edge length $a$ is equal to:

In a crystalline compound,$A$ atoms occupy all corners,$B$ atoms occupy all face-centered positions,$C$ atoms occupy all edge centers,and $D$ atoms occupy all tetrahedral voids formed by $A$ and $B$ atoms. Find the formula of the compound.

$A$ 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?

What is the percentage of unoccupied space in $fcc$ unit cell (in $\%$)?