How many spheres form an octahedral void in a close-packed structure?

In a $ccp$ structure of a mixed oxide,$1/8$ of the tetrahedral voids are occupied by divalent $X^{+2}$ ions and $50\%$ of the octahedral voids are occupied by trivalent $Y^{+3}$ ions. The formula of the oxide is:

In a compound $AB_2O_4$,the oxide ions form a cubic close-packed $(CCP)$ lattice. The molar ratio of trivalent cations to bivalent cations is $2:1$. If all the bivalent ions occupy octahedral voids and trivalent ions occupy both tetrahedral and octahedral voids in equal numbers,then the fraction of octahedral voids that remain unoccupied is:

In an $A_{x} B_{y}$ crystal structure,$A$ atoms occupy all octahedral as well as all tetrahedral voids,and $B$ atoms are at the $FCC$ lattice points. What is the formula of the compound $A_{x} B_{y}$?

An octahedral void is surrounded by how many spheres?

What is the total contribution of all corner particles in a $bcc$ unit cell?