A tungsten atom adsorbed on an atomically smooth tungsten surface can be observed at low temperatures with a field ion microscope. If the sample is heated and then cooled again, the atom has moved by a distance x. The distance x is measured after each of several anneals. The following values of x are observed after repeated 100 second anneals: 0.7, 1.3, 1.0, 0.9, 0.8, 1.5, 1.0 and 1.2 nm. a) Derive an expression for the mean-square displacement of the tungsten atom after n jumps of the tungsten atom for the 2-D random walk. b) Relate the mean-square displacement to the surface diffusion coefficient of the atom. c) Calculate the surface diffusion coefficient of tungsten DW in cm2/s?