Consider a linear object of height h placed in front of a convex lens of focal length f which gives rise to an image of height h₁=4.00 cm on the screen placed at a distance l=10.00 ~cm from the object. Then the lens is shifted towards the screen by a distance d=6.00 cm and again an image of height h₂=9.00 ~cm is observed on the same screen. The ratio of the height to the focal length h / f is