Extracted text: The air shed over a city can be considered by a completely stirred tank reactor (CSTR) model with two sides of 2×10° m in length and a mixing depth of 500 m. Horizontal wind blows at 4 m/s from one side of the box and exits from the opposite side. Assume that within the box, the air is well mixed all the time. Within the air shed, benzene (C6H6) is emitted by automobiles, power plants, and factories at a rate of 0.4 kg/s. No benzene is brought to the city by wind. When equilibrated, what is the benzene concentration in the atmosphere? Please sketch the model first. Pay attention to the units.