A system in its solid phase has a Helmholtz free energy per mole,

a, B/Ty, and in its liquid phase it has a Helmholtz free energy per mole, a = A/Tv, where A and B are constants, v is the volume per mole, and T is the temperature.

(a) Compute the molar Gibbs free energy density of the liquid and solid phases.

(b) How are the molar volumes, v, of the liquid and solid related at the liquid-solid phase transition?

(c) What is the slope of the coexistence curve in the P-T plane?