please help. use distance over velocity for t

5. [ 30 points] A river traveling at a velocity of 10km/ aay nas an initial oxygen deficit of 2mg/L and an ultimate CBOD of 15mg/L. The CBOD has a decay coefficient of 0.3/ day and the stream's reaeration coefficient is 0.4/ day. Assume DOw=9mg/L. a. Assume the conditions above describe Case \#1. Plot the oxygen sag curve in Excel for this condition and show the location of the critical point. Provide the DOmin and ta b. Now assume that the ultimate CBOD increases to 30 mg/L and everything else stays the same (Case \#2). On the same plot as (a) add the new line for Case \#2 and show the location of the new critical point. Provide the DOmin and t-wat for Case \#2. c. Now assume that relative to Case \#1 the reaeration constant is 0.9/ day (Case \#3) and everything else stays the same. On the sample plot as (a), add the new line for Case #3 and show the location of the new critical point. Provide the DOm and t for Case \#3. d. Explain why the curves for (a), (b), and (c) are different. If your calculated values of DO-. and tmowel also changed explain why. Include all graphs and