The winter-kill of fish in mountain lakes has been attributed in part to the depletion of oxygen from the water due to the frozen surface. At the end of the winter, following the thaw, the oxygen concentration in the water in one case was found to be 3x10 kgmol/m'. However, in the spring the water is again oxygenated as a result of its contact with air. If the lake is at an elevation of 2133 m, the concentration of oxygen is 3.08x10 kgmol/m' and is very deep, determine concentration of oxygen in the water at a depth of 0.06 m due to the diffusion after 1 day and determine the penetration distance of oxygen after 30 days. The temperature of the lake is uniform at 5C (D-1.58x10 m2/s). (20 p)