Mark M. answered 03/16/22
Retired math prof. Calc 1, 2 and AP Calculus tutoring experience.
Let x = ticket price and y = attendance
(8, 30000) and (7, 33000) are points on a line
Slope = (33000-30000) / (7-8) = -3000
Equation of line: y - 30000 = -3000(x - 8)
So y = -3000x + 54000 When y = 66000, x = 4 and when y = 0, x = 18
Revenue if price is x: R(x) = (price per ticket)(number of tickets sold) = xy = x(-3000x + 54000)
R(x) = -3000x2 + 54000x, where 4 ≤ x ≤ 18
R'(x) = -6000x + 54000
R'(x) = 0 when x = 9
Maximum revenue when x = $9 per ticket.