The Intensity of Light $I ( d )$ At a Depth D Below the Surface of a Body

Multiple Choice

The intensity of light $I ( d )$ at a depth d below the surface of a body of water changes at a rate proportional to I.If the intensity at a depth of $d = 2.4$ feet is half of the surface intensity $I _ { 0 }$ to the nearest tenth of a foot,at what depth is the intensity $15 \%$ of $I _ { 0 } ?$

A) 6.6 feet
B) 9.9 feet
C) 13.2 feet
D) 7.9 feet