How many unit cells are present in $100 \ g$ of an element with $fcc$ crystal structure having density $10 \ g/cm^{3}$ and edge length $100 \ pm$?

For a crystal, the angle of diffraction $(2 \theta)$ is $90^{\circ}$ and the second order line has a $d$ value of $2.28 \ \text{Å}$. The wavelength (in $\text{Å}$) of $X$-rays used for Bragg's diffraction is

$A$ metal has a $fcc$ lattice. The edge length of the unit cell is $404 \, pm$. The density of the metal is $2.72 \, g \, cm^{-3}$. The molar mass of the metal is ................. $g \, mol^{-1}$.
($N_A$ Avogadro's constant $= 6.02 \times 10^{23} \, mol^{-1}$)

Copper crystallises in $fcc$ structure with a unit cell length of $361 \ pm$. What is the radius of copper atom? ............ $pm$

Bragg's law is given by the equation

What is the atomic mass of an element with $BCC$ structure and density $10 \ g \ cm^{-3}$ having an edge length of $300 \ pm$?