A lens has an index of refraction of 1. 50 . Its left side curves outward with an absolute value of radius of curvature of \(0.15 \mathrm{~m}\), and its right side curves inward with an absolute value of radius of curvature of \(0.25 \mathrm{~m}\). What is its focal length if you look through it \((a)\) from the left side and \((b)\) from the right side?