(Solved): A certain liquid X has a normal boiling point of 137.00C and a boiling point elevation constant ...

A certain liquid $X$ has a normal boiling point of $137.00^{?}\mathrm{C}$ and a boiling point elevation constant $K_b=2.11{}^{?}\mathrm{C}?\mathrm{kg}?\mathrm{mol}{}^{?1}$. A solution is prepared by dissolving some glycine $\left({\mathrm{C}}_2{\mathrm{H}}_5{\mathrm{NO}}_2\right)$ in 400 . $\mathrm{g}$ of $X$. This solution boils at $138.9^{?}\mathrm{C}$. Calculate the mass of ${\mathrm{C}}_2{\mathrm{H}}_5{\mathrm{NO}}_2$ that was dissolved. Round your answer to 2 significant digits.