The magnitudes of power of a biconvex lens (refractive index 1.5) and that of a piano-concave lens (refractive index = l.7) are same. If the curvature of plano-concave lens exactly matches with the curvature of back surface of the biconvex lens, then ratio of radius of curvature of front and back smface of the biconvex lens is________.

A

12:5

B

5:2

C

5:12

D

2:5