At what price should they sell the shirts to maximize revenue?

Question

The 40 Watt can sell 80 shirts per concert if they charge $20 per shirt. They are able to sell 5 fewer shirts for every additional dollar they charge. Assuming the number of shirts they can sell is a linear function of price, at what price should they sell the shirts to maximize revenue?

Answer 1

r represents revenue

x represents each dollar increase

 

r = (80 - 5x)(20 + x)

 

Can you determine the maximum?