Consider the ionic solid AxBy, which has the unit cell below. The B ions are packed in a cubic arrangement, where each face has this structure:

There is one B in the center of the cube. The structure can also be described in terms of three parallel planes of B€™s of the type shown above. The resulting structure thus contains eight intersecting cubes of B€™s. The A ions are found in the centers of alternate intersecting cubes (that is, four of every eight cubes have A€™s in the center). What is the formula of AxBy? In the extended structure, how many B€™s surround each A? What structure do the B€™s form?