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7. (10 points) Layered perovskite materials have become a "hot topic" in research for use as light harvesters in solar cells (see, for example, Snaith, H. J. Phys. Chem. Lett. 2013, 4, 21, 3623–3630). The unit cell for the basic perovskite structure is shown below. Modifications of perovskites for solar cell materials typically replace the Ba?' (pink) cations with small organic cations, which act to break up the layers of TiO octahedra, forming a structure that absorbs visible light. a. Assuming that all ti-o bonds are the same length, to what crystal class does this structure belong? b. Which Bravais lattice does this structure fall under? (Remember that all points in the lattice must be the same!) C. Determine the chemical formula of this perovskite (BaxtiyOz). How many bonds to titanium does each oxygen atom have?