4. To study Brownian motion, Bob, a student at the University of Ottawa, used his camera to capture the positions (i.e. displacements) of 50 microscopic dust particles floating on the surface of the water of his aquarium. By setting his camera to record 10 frames per second and noting down each particle's 2D displacement for each recorded frame, he managed to obtain the following mean-displacement vs time graph: 1600 1400 - 1200 1000 Mean-square disp. (cm?) BOO 600 400 200 0 - 20 40 60 BO 100 120 140 Time (s) a. Use the above mean-displacement graph to roughly approximate the diffusion coefficient D of the dust particles with units of um/s. b. From the diffusion coefficient estimate in a), calculate the root mean- square displacement expected between each consecutive frame? c. Are the diffusion coefficient D and mean-square displacement calculated reasonable for a microscopic particle, or did Bob make a mistake in his