Sunlight is absorbed in water, and as a result the light intensity in oceans, lakes, and ponds decreases exponentially with depth. The percentage of visible light $P$ (in decimal form) at a depth of $x$ meters is given by $P=e^{-k x}$, where $k$ is a constant related to the clarity and other physical properties of the water. The graph shows models for the open ocean, Lake Tahoe, and Lake Erie for data taken under similar conditions. Use these models.
Refer back to Exercise 71 , and find the euphotic depth for Lake Tahoe and for Lake Erie. Round to the nearest tenth of a meter.