A bi-convex lens is formed with two thin plano-convex lenses as shown in the figure. Refractive index $n$ of the first lens is ${\rm{1}}{\rm{.5}}$ and that of the second lens is ${\rm{1}}{\rm{.2}}$. Both the curved surfaces are of the same radius of curvature $R = 14\,\,cm$. For this bi-convex lens, for an object distance of $40\,\,cm$, the image distance will be<br />.