Calculate the potential of a half cell having reaction : ${\mathrm{Ag}}_2\mathrm{S}\left(\mathrm{s}\right)+2{\mathrm{e}}^{-}\rightleftharpoons 2\mathrm{Ag}\left(\mathrm{S}\right)+{\mathrm{S}}^{2-}\left(\mathrm{aq}\right)$ in a solution buffered at p^H=3 and which is also saturated with 0.1MH₂S(aq)
$\text{ [Given : }\left.{\mathrm{K}}_{\mathrm{sp}}\left({\mathrm{Ag}}_2\mathrm{S}\right)=2\times {10}^{-49};{\mathrm{K}}_{\mathrm{a}1}\cdot {\mathrm{K}}_{\mathrm{a}2}=1.1\times {10}^{-21};{\mathrm{E}}_{A{g}^{+}/\mathrm{Ag}}^0=0.8\mathrm{V}\right]$