A point object O is placed at a distance o 20cm from a convex lens of focal 10 cm as shown. At what distance x from lens should a concave mirror of focal length 60 cm can be placed so that final image coincides with object.

Question

$(a)\;20\;cm \\ (b)\;30\;cm \\ (c)\;40\;cm \\ (d)\;50\;cm$