(a) 3 tons of ethanol are accidentally discharged into a lake. By how much is the biological oxygen demand of this water increased? Assume that all ethanol is transformed into CO2 and assume the lake contains 108 liters of water. Explain your answer with the chemical reaction involved and any assumptions you make.

(b) A lake with a cross sectional-area of 1km^2 and a depth of 125 m has an euphotic zone that extends 15 m below the surface, what is the maximum weight of the biomass (in grams of carbon) that can be decomposed by aerobic bacteria in the water column of
the lake below the euphotic zone during the summer when there is no circulation with the upper layer? The bacterial decomposition reaction is (CH2O)n + nO2 --> nCO2 + nH2O The solubility of oxygen in pure water saturated with air at 20ºC is 8.9 mg/L.