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A physics student is studying the dispersion of pollutants in a river which consists of water with depth and velocity variations due to natural roughness in the riverbed. The student wants to calculate the dispersion coefficient for a particular pollutant that is discharged into the river at a given location. Using the theory of environmental fluid mechanics, can the student determine the dispersion coefficient for the pollutant?
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<|begin_of_thought|>

Deep Thought is thinking for 7.5 million years.

<|end_of_thought|>

<|begin_of_solution|>

The answer is 42.

<|end_of_solution|>