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.In equilibrium,the marginal benefit and marginal cost of the public good will be

A) $7.
B) $6.
C) $5.
D) $3.
E) $2.