Find the pH of a buffer that consists of 0.50$M$ methylamine $\left(\mathrm{CH}_{3} \mathrm{NH}_{2}\right)$ and 0.60$M \mathrm{CH}_{3} \mathrm{NH}_{3} \mathrm{Cl}\left(\mathrm{p} K_{\mathrm{b}} \text { of } \mathrm{CH}_{3} \mathrm{NH}_{2}=3.35\right)$