Oxygen levels downstream of a sewage point discharge reach some minimum 'sag' point according to the Streeter-Phelps model as shown in Figure 2. (mg/L) LITHEHEN 10 r (d) 15 20 Figure 2: A dissolved oxygen 'sag below a point of sewage discharge into a river. Streeter-Phelps Model: 0 = 0 North (1) kal e kg-k-ka where o- dissolved oxygen (mg/L), o, - oxygen saturation concentration (mg/L), 7-travel time (d). = biochemical oxygen demand (BOD) concentration at the mixing point (mg/L), k, = rate of decomposition of BOD (d), k-rate of settling of BOD (d), k, -aeration rate (d), and S, - sediment oxygen demand (mg/(L-d)). a) Using prebuilt python functions, write a script that determines what the critical oxygen level will be (minimum oxygen concentration) and when it will occur (i.e. how many days downstream) given the following values: 0 = 10mg ka = 0.1d-, ka = 0.6d, k, = 0.05d, Lo some, L Sp = 1mg/(Ld) b) Plot oxygen concentration over time. c) This point is where lifeforms will be the most stressed; will this level of oxygen support most aquatic life?