To develop strategies to manage water quality in polluted lakes, biologists must determine the depths of sediments and the rate of sedimentation. It has been determined that the depth of sediment D(t) (in centimeters) with respect to time (in years before 1990) for Lake Coeur d’Alene, Idaho, can be estimated by the equation

D(t)=155(1−e−0.0133t).

a. Find D(20) and interpret .

b. Find limt→[infinity]D(t) and interpret.