How do you find a value in steam table which is unknown by interpolation? For example- I would like to find vg = volume

[answerhappygod]

How do you find a value in steam table which is unknown by
interpolation?
For example- I would like to find vg = volume of gaseous
propane per unit mass at initial condition, vf = volume of liquid
propane per unit mass at initial condition, vg = volume of
gaseous propane per unit mass at initial condition vf = volume of
liquid propane per unit mass at initial condition and P1 = initial
pressure of the saturated propane at 23.35°C or 296.5
K and 22.95°C or 296.1 K
In my lab theory, it says that the values of hg, hf, vg, vf, and
P1 could be selected from the propane properties Table for Average
Temperature of the gas cylinder at initial condition.