A Converging Lens with Two Convex Surfaces Has a Front

Multiple Choice

A converging lens with two convex surfaces has a front surface with radius of curvature of 10.0 cm;the back surface has radius of curvature of 20.0 cm,and it is made from material with an index of refraction of 2.50.What is the focal length of the lens?

A) 4.44 cm
B) 13.3 cm
C) -13.3 cm
D) 0.250 cm