Problem 3 a) In a tetragonal crystal, how many symmetry-equivalent crystallographic directions belong to family? Write down all of them. b) In a cubic crystal, how many symmetryequivalent crystallographic planes belong to {211} family? Write down all of them (Since ([1 kl) is identical to (h kl), you need to write down all (h k l) with l > 0) c) For a real body-centered cubic (BCC) crystal (like Fe), write down the correct Miller index of the lattice planes that are perpendicular to [0 1 0] direction and made of real (Fe) atoms. OOOO : b[010]