The Figure Below Shows the Marginal Benefit of Hiring a Security

Multiple Choice

The figure below shows the marginal benefit of hiring a security guard at the airport (MB_A) _, the bank (MB_B) and City Hall (MB_C) . The marginal cost of hiring a security guard is the same at all three places and is given by MC. If each place hires the socially optimal number of security guards, the marginal benefit of the last security guard hired at each place will be the:

A) same at all three places.
B) highest at the airport.
C) highest at the bank.
D) highest at City Hall.