Ray Optics and Optical Instruments Part 2

Two transparent media having refractive indices 1.0 and 1.5 are separated by a spherical refracting surface of radius of curvature 30‌cm. The centre of curvature of surface is towards denser medium and a point object is placed on the principle axis in rarer medium at a distance of 15‌cm from the pole of the surface. The distance of image from the pole of the surface is ______ cm.