50kg of a toxic material is spilled uniformly across a canal. The canal is rectangular with a bottom width of 4.5m and a depth of 1.5m. The discharge in the canal is 15m3/s, and the longitudinal dispersion coefficient is 7m2/s. a. How soon after the spill will the peak concentration be observed 12km downstream of the spill and what will be the maximum concentration at this location? b. plot the concentration as a function of distance at this time (when Cmax is at 12km ) c. if a save level of this contaminent in recreational waters is 15ug/L. At what time after the spill will this concentration first be exceeded, and for approximately how long after that will the water at the downstream location be unsafe? d. what length of canal is contaminated (above 15ug/L ) 2 hours after the spill