The curve \(C\) has equation \(y=\frac{1}{2}\left(\mathrm{e}^{x}+\mathrm{e}^{-x}\right)\) for \(0 \leqslant x \leqslant \ln 5\). Find
(i) the mean value of \(y\) with respect to \(x\) over the interval \(0 \leqslant x \leqslant \ln 5\),

(ii) the arc length of \(C\),

(iii) the surface area generated when \(C\) is rotated through \(2 \pi\) radians about the \(x\)-axis.