The corner points of the feasible region in graphical representation of a L.P.P. are $(2, 72)$, $(15, 20)$ and $(40, 15)$. If $Z = 18x + 9y$ be the objective function, then (A) $Z$ is maximum at $(2, 72)$, minimum at $(15, 20)$ (B) $Z$ is maximum at $(15, 20)$ minimum at $(40, 15)$ (C) $Z$ is maximum at $(40, 15)$, minimum at $(15, 20)$ (D) $Z$ is maximum at $(40, 15)$, minimum at $(2, 72)$