The solubility of barium iodate in an aqueous solution prepared by mixing 200 mL of 0.010 M barium nitrate with 100 mL of 0.10 M sodium iodate is $\mathbf{X} \times 10^{-6}$ moldm ${ }^{-3}$. The value of $\mathbf{X}$ is $\_\_\_\_$ . Use: Solubility product constant ( $K_{\mathrm{sp}}$ ) of barium iodate $=1.58 \times 10^{-9}$