13. Sketch within a cubic unit cell the following planes: (131), (0 11 ), (1 1 2), and (1 0 2). 14. List the individual members of the {110} family of planes for a cubic unit cell. 15. Show that the atomic packing factor for HCP is 0.74. 16. Molybdenum (Mo) has a BCC crystal structure, an atomic radius of 0.1363 nm, and an atomic weight of 95.94 g/mol. Compute its density. 17. Derive linear density expressions for FCC [100] and [111] directions in terms of the atomic radius R. 18. Derive planar density expressions for BCC (100) and (110) planes in terms of the atomic radius R. 19. List close-packed directions and highest-density planes in BCC, FCC and HCP structures. Indicate whether the highest-density planes are close-packed or not.