[QUE/TH-08009] TH-PROBLEM

For a system with two coordinates $PV$ and two other
thermodynamic coordinates $X,Y$
$$ dW = -PdW+YdX $$
a process from state 1 to state 2 at constant temperature and
constant $X$ is possible only if
\begin{eqnarray}
G_1 \le G_2\qquad&\qquad G_1\ge G_2&
\end{eqnarray}