In close packing of N spheres,how many (i)octahedral and (ii)tetrahedral sites are present?

In a close pack array of n spheres, the number of tetrahedral holes are :

Discuss the placing of third layer over the second layer, during close packing in the following two cases: (i) When tetrahedral voids are covered. (ii) When octahedral voids are covered.

How many liver lobes are present in man?

In a cubic close packing of spheres in there dimensions the coordination number of each sphere is:

How many vertebrae are present in a baby ?