What is the total distance between object and image?

A thin, bi-convex lens is to focus an image onto a screen such that the image is life-size. The lens has two equal radii of 120 cm, and a refractive index of n = 1.3.

That's all the info given. I can calculate for focal length and I get 200 cm(correct me if i'm wrong), but don't know what to do from there. The answer, btw, is supposed to 800 cm. Thank you!