The molar conductivity of 0.00241 M acetic acid is $32.87 \mathrm{Scm}^2 \mathrm{~mol}^{-1}$. If the limiting molar conductivity at 298 K is $390.5 \mathrm{Scm}^2 \mathrm{~mol}^{-1}$, what is the dissociation constant ( $\mathrm{mol} \mathrm{L}^{-1}$ )?