Problem 5.28

A point source with luminous intensity $I_{0}=100 \mathrm{~cd}$ is positioned at a distance $s=20.0 \mathrm{~cm}$ from the crest of a concave mirror with focal length $f=25.0 \mathrm{~cm} .$ Find the luminous intensity of the reflected ray if the reflection coefficient of the mirror is $\rho=0.80$