A store in Yosemite National Park charges $6.60 for a flashlight. Approximately 200 of them are sold each week. A survey indicates that the sales will decrease by 10 flashlights per week for each $0.50 increase in price.
a. Write a function that describes the weekly revenue in dollars, y, as a function of selling price in dollars, x.
b. What selling price provides maximum weekly revenue? What is the maximum revenue?