A Store Has Determined That the Weekly Sales of a Product

Multiple Choice

A store has determined that the weekly sales of a product is related to the number of customers who visit the store and the square feet of shelf space, x, according to the following equation: -20x² - 10C² + 40Cx + 120x - 200. C represents the hundreds of customers who visit their store. If a store averages 200 customers per week, how many square feet of shelf space is required to maximize sales?

A) 3
B) 4
C) 5
D) 1 or 9