Answer:
$59
Explanation:
Let the revenue will be maximum when $ x is increased in the ticket price.
So, the final ticket price is $(18 + x) and attendance in the concert will be (500 - 5x)
So, revenue R = (18 + x) (500 - 5x) = 9000 + 410x - 5x².......... (1)
Condition for R to be maximum is

So, differentiating equation (1) with respect to x on both sides

⇒ x = 41
So, the ticket price for maximum revenue is $(18 + 41) = $59 (Answer)