What is the coordination number of a particle in a simple cubic close-packed structure?

$A$ compound formed by elements $X$ and $Y$ crystallises in a cubic structure, where $X$ atoms are at the corners of a cube and $Y$ atoms are at the body centre. The formula of the compound is:

In an ionic crystal with the general formula $AX$,if the coordination number is $6$,what will be the value of the radius ratio?

$A$ solid has a structure in which $W$ atoms are located at the corners of a cubic lattice,$O$ atoms are at the center of the edges,and $Na$ atoms are at the center of the cube. The formula for the compound is:

Copper crystallizes in $f.c.c.$ with a unit cell length of $361 \ pm$. What is the radius of copper atom? (in $pm$)

In the zinc blende structure,zinc atoms fill up: