The concave surface of a thin concavo -convex lens of glass of refractive index`1.5`has a radius of curvature of `20cm`.The concave surface has a radius of curvature of `60cm`.The covnex side is silvered and placed on a horizontal surface as shown in the figure.
A small object is placed on the principal axis of the combination,at a distance of `30cm`in front of the mirror.The magnification of the image is
A. `-(1)/(3)`
B. `(3)/(4)`
C. `5`
D. none of these
