12 The mean value of the function f over the interval \(1 \leq x \leq 5\) is \(m\).
The graph of \(y = \mathrm { g } ( x )\) is a reflection in the \(x\)-axis of \(y = \mathrm { f } ( x )\).
The graph of \(y = \mathrm { h } ( x )\) is a translation of \(y = \mathrm { g } ( x )\) by \(\left[ \begin{array} { l } 3
7 \end{array} \right]\)
Determine, in terms of \(m\), the mean value of the function h over the interval \(4 \leq x \leq 8\)