The corner points of the feasible region determined by a system of linear constraints are $(0, 3)$, $(1, 1)$, and $(3, 0)$. If the objective function is $z = px + qy$, where $p, q > 0$, then the condition on $p$ and $q$ such that the minimum of $z$ occurs at both $(3, 0)$ and $(1, 1)$ is

• A
  $p = 3q$
• B
  $3p = q$
• C
  $p = \frac{q}{2}$
• D
  $p = 2q$