Benzoic acid is a weak acid used as a food preservative. A $0.00800\ \text{mol L}^{-1}$ solution of it in water at $298\ \text{K}$ has a conductivity of $2.63 \times 10^{-4}\ \text{S cm}^{-1}$, after the small conductivity of the water has been taken away. The limiting molar conductivities of three strong electrolytes at $298\ \text{K}$ are, in $\text{S cm}^2\ \text{mol}^{-1}$: HCl 425.9, NaCl 126.4 and sodium benzoate 82.4. The first two values are NCERT's. Use Kohlrausch's law of independent migration of ions, and take the degree of dissociation as $\alpha = \Lambda_m/\Lambda_m^\circ$. Use Ostwald's law in full, $K_a = \dfrac{c\alpha^2}{1 - \alpha}$, keeping the $1 - \alpha$. The dissociation constant of benzoic acid is $K_a = x \times 10^{-6}\ \text{mol L}^{-1}$. What is $x$, to the nearest integer?