A person can see clearly objects only when they lie
between 50 cm and 400 cm from his eyes. In order
to increase the maximum distance of distinct vision
to infinity, the type and power of the correcting lens,
the person has to use, will be :-
(1) concave, - 0.2 diopter
(2) convex, + 0.15 diopter
(3) convex, + 2.25 diopter
(4) concave, - 0.25 diopter