Solve the Problem $\mathrm { L } ( \mathrm { x } )$

Multiple Choice

Solve the problem.
-The intensity $\mathrm { L } ( \mathrm { x } )$ of light $x \mathrm { ft }$ beneath the surface of a lake satisfies the differential equation $\frac { \mathrm { dL } } { \mathrm { dx } } = - 0.07 \mathrm {~L} .$ At what depth, to the nearest foot, is the intensity one tenth the intensity at the surface?

A) 22 ft
B) 49 ft
C) 16 ft
D) 33 ft