The atom at the corner makes \(\frac{1}{8}\) contribution while atom at body centre makes 1 contribution to the unit cell.
No. of atoms of Q per unit cell = 8 × \(\frac{1}{8}\) = 1
No. of atoms of P per unit cell = 1 × 1 = 1
Therefore, formula of the compound is PQ.
The atom at the body centre would be in contact with all the atoms at the corners. Hence, the coordination number of P is 8. Similarly, coordination number of Q is 8 because it is shared by 8 other atoms.