Use the graph of the region corresponding to the system of constraints to find the minimum and maximum values of the objective function subject to the constraints. Identify the points where the optimal values occur. Objective function:
z = 6x + 4y

Constraints:
x 20
y = 0
x + y = 6

The minimum value of
occurs at (x, ) =
The maximum value of
occurs at (x, y) =