$\"\"$

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The weekly revenue function is $\"\"$ , where $\"\"$ is the cost of one sweatshirt.

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(a)

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Find the value of $\"\"$ .

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$\"\"$ .

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Apply derivative on each side with respect to $\"\"$ .

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$\"\"$

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$\"\"$

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Power rule of derivative : $\"\"$ .

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$\"\"$

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$\"\"$ .

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Therefore, the derivative of the function is $\"\"$ .

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$\"\"$

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(b)

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Find the solution for $\"\"$ .

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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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$\"\"$ or $\"\"$

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

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Therefore, the solutions for $\"\"$ are $\"\"$ and $\"\"$ .

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$\"\"$

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(c)

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The solution of $\"\"$ represents the price that Nayla and Deirdre should charge per sweatshirt to make the maximum possible revenue.

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The solution of $\"\"$ is not relevant because the revenue is not equal to zero at $\"\"$ .

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$\"\"$

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(a) $\"\"$

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(b) The solutions for $\"\"$ are $\"\"$ and $\"\"$

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(c) The solution of $\"\"$ represents the price that Nayla and Deirdre should charge per sweatshirt to make the maximum possible revenue.

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The solution of $\"\"$ is not relevant because the revenue is not equal to zero at $\"\"$ .