"Bigtop Productions is hosting the annual outdoor concert. Average attendance is 50 000 people when tickets are $60. For every $20 increase in ticket price, 10 000 fewer people are expected to attend the concert."

14. a) What is the quadratic function in standard form that represents the revenue earned? Be sure to indicate what the variables represent.

b) What admission price will produce the most revenue? Explain how this can be determined.

c) How many people will attend if the maximum revenue is attained?

I was able to find the quadratic function and the solution to b) using the quadratic formula, but I'm unsure about how to get c. Please be thorough in any explanations.