The volume of a glass vessel is 1000 cc at

The volume of a glass vessel is 1000 cc at $20^{\circ} \mathrm{C}$. What volume $v$ of mercury should be poured into it at this temperature so that the volume of the remining space does not change with temperature? Coefficients of cubical expansion of mercury and glass are $1.8^{\times 10^{-4} /{ }^{\circ} \mathrm{C}}$ and $9.0^{\times 10^{-6} /{ }^{\circ} \mathrm{C}}$ respectively.