At the surface of the ocean, the water pressure is the same as the air pressure above the water, $1.05 \mathrm{~kg} / \mathrm{cm}^{2}$. Below the surface, the water pressure increases by $0.3 \mathrm{~kg} / \mathrm{cm}^{2}$ for every $3 \mathrm{~m}$ of descent.
(a) Express the water pressure as a function of the depth below the ocean surface.
(b) At what depth is the pressure $7 \mathrm{~kg} / \mathrm{cm}^{2}$ ?