$3.$ A $30$m$^3$ tank contains $14$ m$^3$

of liquid n$-$butane in equilibrium with its vapor at $25$ deg C$.$

Estimate the mass of n$-$butane $($vapour$,$ liquid and total$)$ in the tank. The vapor pressure of n$-$butane at the given temperature is $2\mathrm{.}43$ bar. Use Pitzer$$s and Rackett$$s equations when applicable.