An Object and a Screen Are Separated by 15

Multiple Choice

An object and a screen are separated by 15.0 cm.A convex lens is placed between them,6.82 cm from the object.In this position it causes a sharp image of the object to form on the screen.What is the focal length of the lens?

A) 4.69 cm
B) 41.0 cm
C) 3.72 cm
D) 12.5 cm
E) 4.09 cm