Consider a lake with volume v and constant inflow and outflow of water, q. a point source load, w, adds a contaminant, c, to the lake at a constant rate (i. e., w is constant). draw a conceptual model for this scenario, write the appropriate differential equation mass balance model, solve the model, and provide a qualitative sketch of c vs time. consider now a point source load that varies linearly with time such that w = at. draw a conceptual model for this scenario, write the appropriate differential equation mass balance model, solve the model, and provide a qualitative sketch of c vs time.