An illuminated point object is placed on the principal axis, in front of an equi-convex glass lens of focal length $$f=40\ \text{cm}$$, at a distance of $$u=1.20\ \text{m}$$ from the lens. A reflecting plane mirror has been placed behind the lens perpendicular to the principal axis and facing the lens. The nature of the final image and the distance of the plane mirror from the lens, so as to form the final image at the plane mirror itself, is