Identical twins anna and hannah visit you at the optical clinic. anna, whose eyes can easily focus on distant objects (her far point), is also able to focus on objects within 20 cm of her eyes (her near point). assuming the diameter and, hence, the distance between the cornea and retina, of anna's eye is 20 mm, what is the range (in diopters) of anna's vision? the limits of this range correspond to the total refractive power of her eyes at their far point and and the refractive power at their near point.

a) from 50 to 50.5 diopters
b) from 50 to 55 diopters
c) from 50 to 60 diopters
d) from 0 to 5 diopters