I really need some help with this one

Question

Darlena has started taking photos at amateur dog racing events, later offering the photos for sale to the dog owners by email. The prices she has charged per photo at each of her first three events, and the corresponding number of photos sold and total revenue raised, appear in the table below.

$52	1	$52
$40	4	$160
$20	9	$180

price per photo ^ number of photos sold^ Revenue^

Treating revenue as a function of the number of photos sold, a graph of the three data points is also shown. If she uses quadratic regression to fit a curve to the data, what number of photos sold and what price per photo will maximize her revenue? 

Answer 1

Look at the peak of the parabola to find the maximum revenue.