If you hold a 900cm squared plane mirror 45 cm from your eyes and can just see the full lenght of an 8.5 m flagpole behind you, how far are you from the pole. I am doing mirror/lens questions and for some reason this one stumps me. im assuming that the 8.5 m has to be changed to cm. However, i have been dealing with questions of radius of curvature and focal length and then this one seems really easy but it has stumped me? can anybody help please?