A solution of $17.1\%$ (w/w) of sucrose (molar mass = $342\text{ g mol}^{-1}$) is isotonic with a $x\%$ (w/w) solution of oxalic acid (molar mass = $90\text{ g mol}^{-1}$). Assume the degree of dissociation of oxalic acid as $0.01$. What is $x$?