What is the coordination number of each atom in a $bcc$ structure?

An ionic compound has a unit cell consisting of $A$ ions at the corners of a cube and $B$ ions on the centres of the faces of the cube. The empirical formula for this compound would be

For an ionic crystal of the type $AB$,the value of the limiting radius ratio is $0.40$. This value suggests that the crystal structure should be:

$A$ cubic unit cell contains manganese ions at the corners and fluoride ions at the centres of each edge. The coordination number of the manganese ion is-

In $NaCl$ type structure, the shortest distance between two nearest neighbours is $100 \ pm$. Then, the distance between two next nearest neighbours in the same unit cell will be:

Total volume of atoms present in a face-centred cubic unit cell of a metal is ($r$ is atomic radius)