An aqueous solution contains $0.10M{H}_{2}S$and 0.20 M HCl.  If the equilibrium constants for the formation of$H{S}^{-}$  from $H_{2}S$ is$1.0\times {10}^{-7}$ and that of $S^{2-}$from $H{S}^{-}$ions is $1.2\times {10}^{-13}$then the concentration of${S^2}^{-}$ ions in aqueous solution is:  (Assuming [H⁺] comes from strong acid only)