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

**(a)**

Find the value of .

.

Apply derivative on each side with respect to .

Power rule of derivative : .

.

Therefore, the derivative of the function is .

**(b)**

Find the solution for .

or

or .

Therefore, the solutions for are and .

**(c)**

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

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

**(a) **

**(b) **The solutions for are and

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

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

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