Find the Maximum Value of the Objective Function and Where $\ge$

Find the maximum value of the objective function and where it occurs, subject to the constraints:
Objective function:

Z = 5x + y

Constraints:

X $\ge$ 0
Y $\ge$ 0
X + 4y $\le$ 20
X + y $\le$ 18
2x + 2y $\le$ 21

A) Maximum at (0, 5) : 5
B) Maximum at $\left( \frac { 22 } { 3 } , \frac { 19 } { 6 } \right)$ : $\frac { 239 } { 6 }$
C) Maximum at (0, 0) : 0
D) No maximum
E) Maximum at $\left( \frac { 21 } { 2 } , 0 \right)$ : $\frac { 105 } { 2 }$