The market demand and supply of electric cars are described by the following equations (Q is quantity of electric cars in units): Demand: P = 1000 1Q thousand dollars per unit Supply: P = 220 3Q thousand dollars per unit Because of causing road congestion, the marginal external cost is 2.5Q 100 thousand dollars when Q electric cars are consumed. On the other hand, because of reducing air pollution caused by the combustion of fossil fuels, for each unit of electric cars consumed, an external benefit of 100 thousand dollars is generated. The unregulated market equilibrium quantity is 195 electric cars. 23. The total economic welfare to the society at the unregulated market equilibrium quantity of electric cars is [ Answer23 = 28518.75 ] thousand dollars