Final answer:
The maximum profit for the t-shirt shop is $5600, and the price charged to reach this maximum profit is $17.50.
Step-by-step explanation:
The profit function for selling each t-shirt at price p is given by the function f(p) = -20p2 + 700p - 2800. To determine the maximum profit, we need to find the vertex of the quadratic function.
The vertex of a quadratic function of the form f(x) = ax2 + bx + c is given by the formula:
x = -b / (2a)
In this case, a = -20 and b = 700. Plugging in these values into the formula, we get:
x = -700 / (2(-20)) = 17.5
So, the price charged to reach the maximum profit is $17.50.
Now, to find the maximum profit, we substitute the value of x into the profit function:
f (17.5) = -20(17.5)2 + 700(17.5) - 2800 = $5600
Therefore, the maximum profit is $5600.