1. The problem statement, all variables and given/known data Question B only 2. Relevant equations 3. The attempt at a solution 1) Why we use f=15.0cm? Shouldn't it be f=infinity considering plane mirror have an infinity focal length? 2) Normally I do combination(lens, mirrors), firstly I will consider the front lens/mirror by finding the 1st image formed. Then the 1st image will be the object of the subsequent lens/mirror. Am I using the right method to do?