Natural organic matter in a lake causes consumption of dissolved oxygen at a rate of 2 mg per day per L. Water entering the lake is saturated with oxygen at a temperature of 20 deg C. The lake has the following properties (based on Lake Greifensee in Switzerland): volumetric flow rate = 0.34×106 m3/day; volume = 150×106 m3; surface area = 8.6×106 m2. If the reaeration rate constant is 0.5 per day, what is the steady state concentration of dissolved oxygen in the lake? Enter your value in units of mg/L with two significant digits.