Linear Programming

The corner points of the feasible region determined by the system of linear constraints are $(0, 10), (5, 5), (15, 15), (0, 20)$. Let $z = px + qy$ where $p, q > 0$. The relation between $p$ and $q$, so that the maximum $z$ occurs at both points $(15, 15)$ and $(0, 20)$ is