Foam products such as shaving cream are made by liquid mixtures whose ingredients are primarily water and

Question:

Foam products such as shaving cream are made by liquid mixtures whose ingredients are primarily water and a refrigerant such as refrigerant-134a. Consider a liquid mixture of water and refrigerant-134a with a water mass fraction of 90 percent that is at 20°C. What is the mole fraction of the water and refrigerant-134a vapor in the gas which fills the bubbles that form the foam?