Use the letters $a$, $b$, $c$, $d$, $j$, and $k$ labeled in the graph below to answer the following questions.

(a) What are the coordinates of the point $P$?
$P =$ help (points)

(b) What are the coordinates of the point $Q$?
$Q =$ help (points)

(c) Evaluate:
$f( c ) =$

(d) Suppose $k = f(z)$ and $z = f(x)$: then
$x =$