A mixture of $100\mathrm{ }\mathrm{m} \mathrm{mol}$ of $\mathrm{Ca}{\left(\mathrm{OH}\right)}_2$ and $2 \mathrm{g}$ of sodium sulphate was dissolved in water and the volume was made up to $100\mathrm{ }\mathrm{mL}.$ What is the mass of calcium sulphate formed and the concentration of ${\mathrm{OH}}^{-}$ in resulting solution, respectively? (Molar mass of $\mathrm{Ca}{\left(\mathrm{OH}\right)}_2,\mathrm{ }{\mathrm{Na}}_2{\mathrm{SO}}_4$ and ${\mathrm{CaSO}}_4$ are $74, 143$ and $136 \mathrm{g}{\mathrm{mol}}^{-1},$ respectively; ${\mathrm{K}}_{\mathrm{sp}}$ of $\mathrm{Ca}{\left(\mathrm{OH}\right)}_2 \mathrm{is}5.5\times {10}^{-6}$)