Problem 5.35

A thin converging lens with focal length $f=25 \mathrm{~cm}$ projects the image of an object on a screen removed from the lens by a distance $l=5.0 \mathrm{~m}$. Then the screen was drawn closer to the lens by a distance $\Delta l=18 \mathrm{~cm} .$ By what distance should the object be shifted for its image to become sharp again?