A person is to be fitted with bifocals. She can see clearly when the object is between 30 cm and 1.5 m from the eye. Assume that the glasses will be worn so that the lenses are 2.0 cm from her eyes. (a) The upper portions of the bifocals should be designed to enable her to see distant objects clearly. What power should they have? (b) The lower portions of the bifocals should enable her to see objects located 25 cm in front of the eye. What power should they have?