TB MC Qu. 14-59 Suppose the market consists of... Suppose the market consists of 3 individuals: Citizen A, Citizen B, and Citizen C. 10 10 10 9 Price ($) Price ($) Price ($) OHNWAMONOD OHNWAMONO OHNWAMONO 0 10 20 30 40 50 0 10 20 30 40 50 0 10 20 30 40 50 Citizen A's Demand Citizen B's Demand Citizen C's Demand If the good shown on the graphs is a public good, and the marginal cost of the 20th unit is $10, then the optimal quantity of the public good is