Find the Maximum Value of the Objective Function and Where $\left( \frac { 22 } { 3 } , 0 \right)$

Find the maximum value of the objective function and where it occurs,subject to the constraints: ?
Objective function:
?
Z = 8x + 9y
?
Constraints:
?
X ? 0
Y ? 0
X + 4y ? 20
X + y ? 18
?2x + 2y ? 21
?

A) Maximum at $\left( \frac { 22 } { 3 } , 0 \right)$ : $\frac { 176 } { 3 }$
B) Maximum at (0,0) : 0
C) Maximum at $\left( 0 , \frac { 19 } { 6 } \right)$ : $\frac { 57 } { 2 }$
D) Maximum at $\left( \frac { 22 } { 3 } , \frac { 19 } { 6 } \right)$ : $$\frac { 523 } { 6 }$$
E) No maximum