Q: The eyepiece of a telescope is a system of two biconvex lenses L1 and L2, of focal length 30 cm and 20 cm respectively, with a separation of 2 cm between them. Lens L2 faces the eye. This eyepiece is to be replaced by a single bi-convex lens L. Which one among the following is the correct combination of the focal length (F in cm) of lens L and its distance from the position of lens L1 (δ in cm)?