${\mathrm{O}}_2$ gas is placed in a 4 litre container contaming 3 L of liquid water as shown and total pressure exerted by gases is 720 mm Hg. What will be the pressure of ${\mathrm{O}}_2\left(\mathrm{g}\right)$ if given container is attached to a empty container of 3 litre at same temperature?  Given: $\text{ [V.P. of }{\mathrm{H}}_2\mathrm{O}\text{ at }{27}^{\circ }\mathrm{C}=20\mathrm{mm}\text{ of }\mathrm{Hg}\text{ ] }$