How many unit cells share a corner of a unit cell in a crystal lattice?

$A$ compound is formed by two elements $A$ and $B$. The element $B$ forms a cubic close-packed $(CCP)$ structure and atoms of $A$ occupy $\frac{1}{3}$ of the tetrahedral voids. If the formula of the compound is $A_x B_y$,then the value of $x+y$ is:

What is the total number of tetrahedral voids in $0.6 \ mole$ of a compound that forms a $hcp$ structure?

$A$ compound forms an $hcp$ structure. What is the total number of tetrahedral voids formed in $0.8 \text{ mol}$ of this compound?

The fraction of the total volume occupied by the atoms in a simple cubic unit cell is

What is the type of hole occupied if the limiting value of $\frac{r+}{r-}$ is in the range of $0.225$ to $0.414$?