Please help me with these ones asap I don't get it, will rate thanks

11. For cubic crystals, as values of the planar indices h, k, and I increase, does the distance between adjacent and parallel planes (i.e., the interplanar spacing, dhki) increase or decrease? Explain in simple terms using Equation 3.22. 12. Niobium metal is BCC and has an atomic radius of 0.146 nm. Compute the interplanar spacing for the (212) set of planes in nm. 13. The metal Silver (Ag) has an FCC crystal structure. If the angle of diffraction for the (111) set of planes occurs at 20 = 38.3182 (first-order reflection, n = 1) when monochromatic x- radiation having a wavelength of 0.15056 nm is used, compute (a) the interplanar spacing for this set of planes, and (b) the atomic radius for an Ag atom