A $75 \mathrm{mL}$ solution that is $0.10 \mathrm{M}$ in ${\mathrm{HC}}_2{\mathrm{H}}_3{\mathrm{O}}_2$ $0.10 \mathrm{M}$ in ${\mathrm{NaC}}_2{\mathrm{H}}_3{\mathrm{O}}_2$ has a pH of $4.74.$ Which of the following actions will change the pH of this solution?

(P) Adding 15 mL of $0.10 \mathrm{M} \mathrm{HCl}$

(Q) Adding $0.010 \mathrm{mol}$ of ${\mathrm{NaC}}_2{\mathrm{H}}_3{\mathrm{O}}_2$

(R) Diluting the solution from 75 mL to 125 mL