Which of the following statements is true?
(1) A convex lens with power +4D has a focal length –0.25 m.
(2) A convex lens with power –4D has a focal length + 0.25.
(3) A concave lens with power +4D has a focal length + 0.25.
(4) A concave lens with power –4D has a focal length –0.25 m.