In an astronomical telescope, the distance between the objective and the eyepiece is 36 cm and the final image is formed at infinity. The focal length f₀ of the objective and the focal length f_e the eye piece are
1) ${\mathrm{f}}_0=45\mathrm{cm}\text{ and }{\mathrm{f}}_{\mathrm{e}}=-9\mathrm{cm}$
2) ${\mathrm{f}}_0=50\mathrm{cm}\text{ and }{\mathrm{f}}_{\mathrm{e}}=10\mathrm{cm}$
3) ${\mathrm{f}}_0=7.2\mathrm{cm}\text{ and }{\mathrm{f}}_{\mathrm{e}}=5\mathrm{cm}$
4) ${\mathrm{f}}_0=30\mathrm{cm}\text{ and }{\mathrm{f}}_{\mathrm{e}}=6\mathrm{cm}$