How To find Coordination Number (NN) , NNN of SCC and BCC unit Cell

The coordination number and number of carbon atoms in a unit cell of diamond is :-

The coordination number for an atom in a primitive cubic unit cell is :

The coordination number of each atom in body centered cubic unit cell is

A metal can be crystallized in both BCC and FCC unit cells whose edge lengths are 2 pm and 4 pm respectively. Then ratio of densities of FCC and BCC unit cells is