Kemilyn and Weston each write the equation of the inverse function for $h(x) = \frac { x - 5 } { x + 4 }$, but they come up with different equations for the inverse. Kemilyn thinks $h^{−1}(x) = \frac { 4 x + 5 } { 1 - x }$, but Weston thinks $h^{−1}(x) = \frac { - 4 x - 5 } { x - 1 }$. Who is correct? Justify your answer.