Table: Security in a Residential Community Quantity of security Total Individual guards Cost benefit 0 $0 $0 1 150 10 2 300 16 3 450 18 4 600 19 The accompanying table shows the total cost of hiring a 24-hour security service and each individual resident's total benefit from the service in a residential community of 100 residents. The efficient number of security guards is 0 2 0 3 0 4