Scenario 10-1 The demand curve for gasoline slopes downward and the supply curve for gasoline slopes upward. The production of the 1,000th gallon of gasoline entails the following: a private cost of $3.10; a social cost of $3.55; a value to consumers of $3.70. Refer to Scenario 10-1. The production of the 1,000th gallon of gasoline entails an a. external benefit of $0.15. b. external cost of $0.15. c. external benefit of $0.45. d. external cost of $0.45