A person can see objects clearly only if they are between 0.6 m and 4 m from her eyes. Her optometrist prescribes bifocals that enable her to see distant objects through the top half of the lenses and read papers at a distance of 0.25 m through the lower half. What are the respective powers of the top and bottom lenses?
a. -0.25 dB (top lens); +5.7 dB (bottom lens)
b. +2.3 dB (top lens); -3.3 dB (bottom lens)
c. +4 dB (top lens); -1.7 dB (bottom lens)
d. -5.7 dB (top lens); +0.25 dB (bottom lens)
e. -0.25 dB (top lens); +2.3 dB (bottom lens)
