How does the structure of $NaCl$ transform into the $CsCl$ structure?

The empirical formula for a compound with a cubic close packed arrangement of anions and with cations occupying all the octahedral sites is $A_{x}B$. The value of $x$ is ..... .
(Integer answer)

The packing efficiency and coordination number of face-centred cubic $(FCC)$ lattice is

In a face centered cubic lattice,atoms $A$ are at the corner points and atoms $B$ are at the face centered points. If one atom $B$ is missing from one of the face centered points,the formula of the ionic compound is:

The number of hexagonal faces that are present in a truncated octahedron is

Coordination numbers of $Zn^{2+}$ and $S^{2-}$ in the crystal structure of wurtzite are