Sets $A$, $B$, and $C$ are defined as
$$\begin{aligned}& A = \{ ( x , x ) : x \in \mathbb { R } \} \\& B = \{ ( x , 3 - x ) : x \in \mathbb { R } \} \\& C = \{ ( x , x + 4 ) : x \in \mathbb { R } \}\end{aligned}$$
Given that $( p , q ) \in A \cap B$ and $( r , s ) \in B \cap C$,
$$\frac { p - r } { q + s }$$
what is the value of this expression?\
A) $\frac { 1 } { 3 }$\
B) $\frac { 1 } { 4 }$\
C) $\frac { 3 } { 4 }$\
D) $\frac { 4 } { 5 }$\
E) $\frac { 2 } { 5 }$