P_a and P_b Represent the Prices That Citizens (A)and (B),the

P_a and P_b represent the prices that citizens (a) and (b) ,the only two people in this nation,are willing to pay for additional units of a quantity (Q_c) of the public good.Q_s represents the quantity of the public good supplied by government at each of the collective prices. Refer to the above information.If the collective willingness to pay for an additional unit of this public good is $6,then the collective quantity demanded will be:

A) 1 unit and the socially optimal quantity supplied will be 5 units.
B) 2 units and the socially optimal quantity supplied will be 4 units.
C) 3 units and the socially optimal quantity supplied will be 3 units.
D) 4 units and the socially optimal quantity supplied will be 2 units.