The diagram shows the graph of \(y = f^{-1}(x)\), where \(f^{-1}\) is defined by \(f^{-1}(x) = \frac{1 - 5x}{2x}\) for \(0 < x \leq 2\).

(i) Find an expression for \(f(x)\) and state the domain of \(f\).

(ii) The function \(g\) is defined by \(g(x) = \frac{1}{x}\) for \(x \geq 1\). Find an expression for \(f^{-1}g(x)\), giving your answer in the form \(ax + b\), where \(a\) and \(b\) are constants to be found.