To find the market demand for a good or service, economists: Please choose the correct answer from the following choices, a) subtract the quantities of a good or service each consumer would buy at each price from the total number of goods available to sell. b) add together the prices each consumer would pay for each quantity of a good or service. c) add together the quantities of a good or service each consumer would buy at each price. d) perform the process called vertical summation of the individual demand curves.