An experiment is performed to calculate the focal length of a convex mirror using convex lens. The setup consists of two pins, optical bench, one convex lens and one convex mirror. When only convex lens is placed at a distance 60cm from pin (object) its image is formed at a distance 30cm from the lens as shown in figure (i) now.  Convex mirror is also kept right to the lens without changing distance between pin (object) and lens. The mirror at a distance 10cm from lens such that position of image of object pin and position of object pin coincides as shown in figure (ii)

 

Now answer the following questions.