Please answer only question 5 NOT 4.

4. For a surface water sample, we measured the water quality that shows pH=6.5, alkalinity=250 mg/L as CaCO₃, hardness=150 mg/L as CaCO₃, TDS=50 mg/L; temperature=298 k; Ca²⁺=100 mg/L. please calculate (1) Langelier index; (2) Aggressive Index; (3) Ryznar Index. Then, determine if water is corrosive or tend to form scale.

5. Following the question 4, please plot a graph showing the changes of the three indexes when the hardness level increases from 0 to 300 mg/L as CaCO₃ and discuss which index you think is most sensitive to the variations of hardness level. Hint: you can enter the same parameters as you did for question 4 except that you change hardness at a time to obtain specific values of the three indexes and save the data in excel. Repeat this operation to obtain several data points to cover the range of hardness (0-300) and plot a graph using excel to combine all the three indexes. The trend curve that has the highest slope is considered the most sensitive.