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Problem 4 (15 points): Fick's first diffusion law states that dc Mass flux =-D dx = = Where mass flux = the quantity of mass that passes across a unit area per unit time (g/cm2/s), D = a diffusion coefficient (cm²/s), c = concentration (g/cm), and x distance (cm). An environmental engineer measures the following concentration of a pollutant in the pore waters of sediments underlying a lake (x = 0 at the sediment-water interface and increases downward): x, cm 0 1 3 C, 10-ºg/cm3 0.06 0.32 0.6 Use the best numerical differentiation technique available to estimate the derivative at x = 0. Employ this estimate in conjunction with above equation to compute the mass flux of pollutant out of the sediments and into the overlying waters (D = 1.52 x 10 cm</s). For a lake with 3.6 x 10º m? of sediments, how much pollutant would be transported into the lake over a year's time? =