A piece of thin spherical shell that has a radius of curvature of 90 cm is silvered on both sides. The concave side of the piece forms a real image 67.5 cm from the mirror. The piece is then turned around so that its convex side faces the object. The piece is moved so that the image is now 35 cm from the piece on the concave side.
(a) How far was the mirror moved?
= cm