You are an environmental scientist who has been hired to assess the damge caused by an accident in which an eyeglass lens manufacturer, located on a river, released acetone directly into the water. Fortunately, only one 5.0-L bottle was released. The river has an average depth of 10 m, a width of 45 m and longitudinal dispersion coefficient of 49.7 m^2/sec. The water velocity is estimated to be 3.0 m/sec. Acetone has a density of 0.786 gm/mL and a half-life in water of 20.0 hr. Determine the concentration of acetone in the river due to this pulse release at distance of 2, 4, and 7 km from the site at times of 5, 15, 20, and 30 hr.