The solvent $CS_2$ has enthalpy of vapourization of $352\;J\;g^{-1}$ and boiling point equal to $320\;K$. The value of $K_b$ for this solvent is about.

Question

$\begin{array}{1 1} 0.51\;K\;kg\;mol^{-1}\\0.86\;K\;kg\;mol^{-1} \\ 1.23 \;K\;Kg\;mol^{-1} \\ 2.42\;K\;kg\;mol^{-1} \end{array}$