$3.)$ Calculate the concentrations of all molecular and ionic species and the $pH$ in aqueous solutions that have the following formal compositions:

a$)0\mathrm{.}05M$ acetic acid $+0\mathrm{.}1M$ sodium acetate;

b$)0\mathrm{.}2M$ boric acid $+0\mathrm{.}05M$ sodium borate of boric acid $($:$=9\mathrm{.}24\}$;

c$)0\mathrm{.}5M$ hydrochloric acid.