The conductivity of a weak acid HA of concentration $0.001 \mathrm{~mol} \mathrm{~L}^{-1}$ is $2.0 \times 10^{-5} \mathrm{~S} \mathrm{~cm}^{-1}$. If $\Lambda_{\mathrm{m}}^{\circ}(\mathrm{HA})=190 \mathrm{~S} \mathrm{~cm}^2 \mathrm{~mol}^{-1}$, the ionization constant (Ka) of HA is equal to $\_\_\_\_$ $\times 10^{-6}$. (Round off to the Nearest Integer)