Find the Minimum Value of the Objective Function and Where $$\left( \frac { 21 } { 2 } , 0 \right)$$

Multiple Choice

Find the minimum value of the objective function and where it occurs,subject to the constraints: ?
Objective function:
?
Z = 8x + y
?
Constraints:
?
X ? 0
Y ? 0
X + 4y ? 20
X + y ? 18
?2x + 2y ? 21
?

A) Minimum at (0,0) : 0
B) Minimum at (5,0) : 40
C) Minimum at $$\left( \frac { 21 } { 2 } , 0 \right)$$ : 84
D) Minimum at (18,0) : 144
E) No minimum