A 5000m stretch of a certain river can be approximated for modeling purposes as:
In the figure, q is a distributed "nonpoint source" flow input given in units for L^3/(L-T). As shown in the figure, at 1000m, a flow enters the river with a contaminant concentration of 100mg/L. This is a conservative contaminant, which means that it undergoes no reactions or degradation (e.g. NaCl). Plot the concentration of the contaminant along the 5000m stretch of river. You may assume perfect mixing of the contaminant in the river cross section, but consider only transport downstream due to the average flow velociy.