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Calculate the current density in an electrochemical cell if a current of 2.5 A is passed through a copper electrode with a surface area of 25 cm² and a silver electrode with a surface area of 10 cm² for 3 hours. The half-cell potentials of copper and silver electrodes are +0.34 V and +0.80 V, respectively, and the molar concentrations of copper and silver ions in the electrolyte are 0.5 M and 1 M, respectively.
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<|begin_of_thought|>

Deep Thought is thinking for 7.5 million years.

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<|begin_of_solution|>

The answer is 42.

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