Buffer Solutions

What will be the $\mathrm{pH}$ of solution formed by mixing $10 \mathrm{mL}0.1{\mathrm{MNaH}}_2{\mathrm{PO}}_4$ $15 \mathrm{mL}$ $0.1{\mathrm{MNa}}_2{\mathrm{HPO}}_4$
[Given: $\left.{\mathrm{pK}}_1=2.12,{\mathrm{pK}}_2=7.2\right]$

For a buffer of a mixture of $0.12 \mathrm{mol} {\mathrm{L}}^{-1}$ ${\mathrm{CH}}_3\mathrm{COOH}$ and $0.12 \mathrm{mol} {\mathrm{L}}^{-1}{\mathrm{CH}}_3\mathrm{COONa},$ the buffer capacity is