Suppose the recreational demand function for a beach is given by: x = 4 - (C/500) + q. The number of visits is represented by x, travel cost in dollars is represented by C, and water quality in units is represented by q. Now, suppose a public project to clean up the beach improves water quality from 0 to 2 units (thus, q = 2). The estimated benefit of the project to beach visitors is equal to $______