\textbf{220.} The solubility of lead(II) chloride at a certain temperature is $1391\,\mathrm{g}$ per $100\,\mathrm{g}$ of water. The concentration of the solution at this temperature is $1\,\mathrm{g.mL^{-1}}$ (density of water). Which value of $\mathrm{mol.L^{-1}}$ is correct?
$$(\mathrm{Pb} = 207.2 \quad \mathrm{Cl} = 35.5\,:\,\mathrm{g.mol^{-1}})$$
(1) $\Delta \times 10^{-3}$ \quad (2) $5\times10^{-4}$ \quad (3) $5.7\times10^{-4}$ \quad (4) $5.7\times10^{-4}$
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