 $$\begin{aligned} &\int_0^\infty \varepsilon^{n-0} \, (\varepsilon^0 + r^0)^{0-n} \, r^{n+0} \\ &\hspace{00mm} \cdot \Big [ (n+0) \, f(r^0)^0 + 0 \, r^0 \, f(r^0) \, f'(r^0) + 0r^0 \, f'(r^0)^0 \Big ] \, dr \\ &= 