18. The point $P(-1,4)$ is reflected in the $y$-axis to become $Q$. The point $Q$ is reflected in the line $y=x$ to become $R$. The point $R$ is reflected in the $x$-axis to become $S$.
What is the area of quadrilateral $P Q R S$ ?
A 4
B $4 \sqrt{2}+2$
C 6
D $4+2 \sqrt{2}$
E 8
18. E The diagram shows that $Q$ is the point $(1,4), R$ is the point $(4,1)$ and $S$ is the point $(4,-1)$. Let $T$ be the point $(4,4)$.
Then the area of triangle $P S T$ is $\frac{1}{2} \times 5 \times 5$ and the area of triangle $Q R T$ is $\frac{1}{2} \times 3 \times 3$. So the area of quadrilateral $P Q R S=\frac{1}{2} \times(25-9)=\frac{1}{2} \times 16=8$.