Q$3(30$ pts$).$ Consider a $50\mathrm{.}0mL$ of $0\mathrm{.}100M$ sodium hydrogen oxalate $($NaHA$)$ solution.

For oxalic acid $(H_2(A)),K_{a1}=5\mathrm{.}60{10}^{-2},K_{a2}=5\mathrm{.}42{10}^{-5}.$

a$)$ What is the $pH$ of the solution?

b$)$ What will be the $pH$ when $20\mathrm{.}1mL$ of $0\mathrm{.}250$MNaOH is added to $50\mathrm{.}0mL$ of $0\mathrm{.}100$MNaHA solution?

c$)$ What will be the $pH$ when $5\mathrm{.}0mL$ of $0\mathrm{.}250MHCl$ is added to $50\mathrm{.}0mL$ of $0\mathrm{.}100$MNaHA solution?