A point object O is placed in front of a plane mirror and plano – convex lens (whose convex side is silvered) assembly, as shown. Find the distance d (in cm) of the object from the plane mirror so that the final image is created at the itself. Radius of curvature of the convex side of plano – convex lens is 42 cm and its refractive  index is  $\frac{3}{2}$.