Marine life is dependent upon the microscopic plant life that exists in the photic zone, a zone that goes to a depth where about 1% of the surface light remains. In some waters with a great deal of sediment, the photic
zone may go down only 15 or 20 feet. In some murky harbors, the intensity of light d feet below the surface is
given by I = 1o e -0.18d, where lo is the intensity of light at the surface. What percentage of the surface light will
reach a depth of
(A) 10 feet? (B) 20 feet?