The \( \mathrm{OH^-} \) concentration in a mixture of \( 5.0 \, \mathrm{mL} \) of \( 0.0504 \, \mathrm{M} \) \( \mathrm{NH_4Cl} \) and \( 2 \, \mathrm{mL} \) of \( 0.0210 \, \mathrm{M} \) \( \mathrm{NH_3} \) solution is \( x \times 10^{-6} \, \mathrm{M} \). The value of \( x \) is __________. (Nearest Integer)
[Given \( K_w = 1 \times 10^{-14} \) and \( K_b = 1.8 \times 10^{-5} \)]
