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

The volume of atoms (radius r) present in fcc unit cell of metal is:

Question 1
If the radius of a sphere is 2r, then its volume will be:

A) $\frac{4}{3}\pi r^3$
B) $4\pi r^3$
C) $\frac{8}{3}\pi r^3$​​​​​​​
D) $\frac{32}{3}\pi r^3$​​​​​​​

Total volume of atoms present in a face centred cubic unit cell of a metal is (r = radius of atom).