$\"\"$

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$\"\"$ ,where $\"\"$ is measured in years and $\"\"$ is measured in dollars per year,

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The total revenue obtained in the first four years is $\"\"$ .

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$\"\"$

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Evaluate $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$ $\"\"$ .

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$\"\"$

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The revenue is $\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$ .

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$\"\"$

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$\"\"$ .