The city of Greenville has 10 residents who each have the following identical willingness- to-pay functions for open space: WTP = 50 – 20, where Q is acres of open space. The marginal cost of maintaining the open space is MC = 80 +Q. If the city of Greenville provides public access to the open space, all of the residents can enjoy the area.

(a) What is the socially optimal acreage of open space in Greenville?