The following waters that are treated with a feeric chloride dose of $40$ mg$/$L

a$.$ Water A has an initial alkalinity of $136$ mg$/$L as CaCO$3$ and an initial pH of $7\mathrm{.}6.$What is the final alkalinity and pH$?$

b$.$ Water B has an initial alkalinity of $0$ mg$/$L as CaCO$3$ and an initial pH of $7\mathrm{.}6.$ What is the final alkalinity and pH$?$ How much slaked lime $($calcium hydroxide$)($mg$/$L$)$ would be required to maintain the initial pH of $7\mathrm{.}6?$

c$.$ Water C has an initial alkalinity of $20$ mg$/$L as CaCO$3$ and an initial pH of $7\mathrm{.}6.$What is the final alkalinity and pH$?$ How much soda ash $($sodium carbonate$)($mg$/$L$)$ would be required to maintain the initial pH of $7\mathrm{.}6?$