interstitial voids

A solid made up of ions of A and B possess edge length of unit cell of 0.5664nm has four formula units. Among the two ions, the smaller one occupy the interstitial void and the larger ions occupy the space lattice with ccp type of arrangement. One molecule of solid has mass 9.712xx10^(-23)g. The co - ordination number of solid is :

A solid made up of ions of A and B possess edge length of unit cell of 0.5664nm has four formula units. Among the two ions, the smaller one occupy the interstitial void and the larger ions occupy the space lattice with ccp type of arrangement. One molecule of solid has mass 9.712xx10^(-23)g. Which statement is wrong about solid is :