Grade 12 calculus, derivatives. Show your work

Question 2 (8 points) The current ticket price at a local theatre is $4, and the theatre attracts an average of 250 customers per show. For every 20 cent increase in ticket price, the average attendance reduces by 10 customers, while every 20 cent decrease results in 10 extra customers. The theatre has a maximum capacity of 400. Determine the ticket price that will maximize revenue for the theatre. A/