Ive been trying to figure this one out for too long,please help :s !!!

Molar volume of a saturated vapour-liquid system is given by V=Vf(1-X) + VgX,

where Vf=molar vol. of condensed phase

Vg=molar volume of vapour phase

X=quality

A given closed system contains only water in VLE at 25oC. Vapour pressure of water at this temp. is 3168 Pa.

Calculate the molar volume of the system if the quality is 0.2.

Any ideas??

Thanks