At the surface of the ocean, the water pressure is the same as the air pressure above the water, 15 $ lb/in^2 $. Below the surface, the water pressure increases by 4.34 $ lb/in^2 $ for every 10 ft of descent.
(a) Express the water pressure as a function of the depth below the ocean surface.
(b) At what depth is the pressure 100 $ lb/in^2 $?