A Double Concave Lens Has Radii of Curvature of 15

A double concave lens has radii of curvature of 15.0 cm and 10.0 cm. An object placed 14.0 cm from the lens forms a virtual image, twice as large as the object. The index of refraction of the material the lens is made of is

A) 2.80.
B) 1.50.
C) 1.21.
D) 1.07.
E) 1.33.