Correct. Since the maximum profit will coincide with the vertex of the quadratic's parabola, you can use the vertex to find the maximum profit. The x-axis represents selling price, so the value of the x-coordinate at the vertex represents the best price. Plugging the a and b values from the equation into the formula $\displaystyle{x}=\frac{{-{b}}}{{{2}{a}}}\usepackage{cmbright}\Huge\$ , you find $\displaystyle{x}=\frac{{-{50}}}{{{\left({2}\right)}{\left(-{2}\right)}}}={12.5}\usepackage{cmbright}\Huge\$ .