Line $p$ has equation $y=x+3,$ and line $q$ has equation $y=x-1$.
a. Find the equation of a line $r$ that is perpendicular to $p$ and $q .$
b. Find the coordinates of the intersection of $p$ and $r$ and the coordinates of the intersection of $q$ and $r$.
c. Find the distance between lines $p$ and $q$.