A parallel beam of white light falls on a convex lens. Images of blue, yellow and red light are formed on other side of the lens at a distance 20 cm, 20.5 cm and 21.4 cm respectively. The dispersive power of the material of the lens will be

Options

A. `619/1000`
B. `9/200`
C. `14/205`
D. `5/214`.