A student uses a convex lens as a simple magnifier during a laboratory activity.
a. (i) The focal length of the lens is 5cm. Determine the magnifying power obtained when the final image is at infinity for a normal eye whose least distance of distinct vision is 25cm.
b. (ii) If the same lens is used by a child whose near point is 20cm, calculate the magnifying power under identical viewing conditions (final image at infinity).