Similar Ideal Gas Law question

[MastersBound]

Homework Statement

A 500 m^3 tank is filled with saturated liquid-vapor mixture of water at 200 kPa. If 20% percent of mass is liquid and 80 percent of the mass is vapor, the total mass in the tank is?

Homework Equations

pV=mRT

The Attempt at a Solution

Don't have a clue... sorry

 

[vela]

Start by looking up the specific volume of water for the two phases in a table.