A hypothetical AX type material is known to have a density of 2.10 g/cm 3 and a unit cell of cubic symmetry with a cell edge length of 5.7Å. The atomic weights of the A and X elements are 28.5 and 30 /mole, respectively. On the basis of this information, which of the following crystal structures is(are) possible for this material: sodium chloride, cesium chloride, or zinc blende? Justify your answer.