The distance of the lens in the human eye from the retina, on which the image is focused, is about 1.7 cm. To focus on a book 63.7 cm from the eye,

The distance of the lens in the human eye fromthe retina, on which the image is focused, isabout 1.7 cm.To focus on a book 63.7 cm from the eye,what must the focal length of the eye be?Answer in units of cm