Suppose that the marginal benefit of having a security guard at the airport is MB1,at the bank is MB2,and at the mall is MB3.The marginal cost of assigning security guard is the same for all three places,and it is represented by MC2.
The optimal number of security guards at the airport is ____,the optimal number of security guards at the bank is _______,and the optimal number of security guards at the mall is ______.
A) 3;3;6
B) 6;4;3
C) 5;4;2
D) 6;5;4