K_a for CH_3 COOH is 1.8 × 10^-5 and K_b for NH_4 OH is 1.8 × 10^-5. The pH of ammonium acetate solution will be ____.

$\displaystyle \mathrm{K}_{\mathrm{a}}$ for $\displaystyle \mathrm{CH}_3 \mathrm{COOH}$ is $\displaystyle 1.8 \times 10^{-5}$ and $\displaystyle \mathrm{K}_{\mathrm{b}}$ for $\displaystyle \mathrm{NH}_4 \mathrm{OH}$ is $\displaystyle 1.8 \times 10^{-5}$. The pH of ammonium acetate solution will be $\displaystyle \_\_\_\_$.