A certain liquid X has a normal freezing point of $4\mathrm{.}20\backslash$deg C and a freezing point depression constant $=$Kf$4\mathrm{.}97\backslash$deg C$$kgmol$1.$ A solution is prepared by dissolving some ammonium sulfate $($NH$42$SO$4)$ in $400.$g of X$.$ This solution freezes at $0\mathrm{.}4\backslash$deg C$.$ Calculate the mass of NH$42$SO$4$ that was dissolved.

Round your answer to $2$ significant digits.