The Figure Below Shows the Marginal Benefit of Having a Security

Multiple Choice

The figure below shows the marginal benefit of having a security camera at the library (MB_L) , the supermarket (MB_S) , and the museum (MB_M) . The marginal cost of hiring a security guard is the same at all three places and is given by MC. The optimal number of security cameras is ______ at the library, ______ at the super market, and ______ at the museum.

A) 2; 5; 8
B) 4; 4; 4
C) 8; 5; 2
D) 5; 8; 11