How many atoms are there in a cube-based unit cell,having one atom on each corner and $2$ atoms on each body diagonal of the cube?

$A$ solid compound contains atoms $X, Y,$ and $Z$. In its unit cell,atoms $X$ are at the corners,atoms $Y$ are at the body center,and atoms $Z$ are at the face centers. The formula of the compound is:

The coordination number of a sphere in a face-centered cubic $(fcc)$ lattice is .....

What are the coordination numbers of $bcc$,$scc$,and $fcc$ respectively?

The structure of $MgO$ is similar to $NaCl$. What would be the coordination number of magnesium?

In a compound formed by $A^{+}$ and $B^{-}$ ions,$B^{-}$ ions are arranged at all corners except two and at all face centers except three,while $A^{+}$ ions are at the midpoints of all body diagonals. The molecular formula of the compound will be ................