The \({\mathrm{OH}}^{-}\)concentration in a mixture of \(5.0\mathrm{mL}\) of \(0.0504\mathrm{M}\) \({\mathrm{NH}}_{4}\ma…

The \({\mathrm{OH}}^{-}\)concentration in a mixture of \(5.0\mathrm{mL}\) of \(0.0504\mathrm{M}\) \({\mathrm{NH}}_{4}\mathrm{Cl}\) and \(2\mathrm{mL}\) of \(0.0210M{\mathrm{NH}}_{3}\) solution is __________\(\mathrm{x}\times {10}^{-6}\mathrm{M}\). The value of \(\mathrm{x}\) is . (Nearest integer)

[Given \({\mathrm{K}}_{\mathrm{w}}=1\times {10}^{-14}\) and \({\mathrm{K}}_{\mathrm{b}}=1.8\times {10}^{-5}\) ]

[JEE Main 2021, 26 Aug (Shift 1)]