Which of the following is true of consumer surplus? a. It is graphically represented as the area under the equilibrium price and above the supply curve of a good . b. It is t he net gain in economic well-being associated wit h producing and selling the equilibrium quantity of a good. c. It is u sed to measure the im pa ct of a change in pri ce on the economic well-being of the producers. d. It is the difference between the value that one place s on a good and the price paid for the good .