A volume occupied by a saturated vapour is reduced isothermally n-fold. Find what fraction of the final

Question:

A volume occupied by a saturated vapour is reduced isothermally n-fold. Find what fraction η of the final volume is occupied by the liquid phase if the specific volumes of the saturated vapour and the liquid phase differ by N times (N > n). Solve the same problem under the condition that the final volume of the substance corresponds to the midpoint of a horizontal portion of the isothermal line in the diagram p, V.