Crystallization is the process of forming crystals from a solution. Strictly speaking, it is one of the techniques used to separate a "solid" from a solution.To perform crystallization, usually the temperature is lowered, thus decreasing the solubility of the solid in the solution. An alternative process is to remove water by evaporation. A solution contains $20\mathrm{.}0\%$ w$/$w Na$,$SO$,,15\mathrm{.}0\%$ w$/$w Na$,$CO;$,$ with the rest being water. This solution is passed through an evaporator that removes $10\mathrm{.}0\%$ of the original mass and then crystallizes $20\mathrm{.}0\%$ Na$2$SO$,$ and $30\mathrm{.}0\%$ NaCO. The crystals formed are Na$,$CO$,$ per ten molecules of H$20$ and NazSO$4$ per ten molecules of H$2$O$.$ Calculate the composition of the residual solution.