If the feasible region is unbounded, then
(i) M is the maximum value of the objective function, if the open half plane
determined by ax + by > M has no point in common with the feasible
region Otherwise, the objective function has no maximum value (ii) m is the minimum value of the objective function, if the open half plane
determined by ax + by < m has no point in common with the feasible
region Otherwise, the objective function has no minimum value