The alternative to voluntary exchange is:

Central planners in command economies

a. generally set production targets for firms. b. always consult consumers on the output of goods they want to consume. c. allow prices to organize the economy's production. d. depend upon the invisible hand to coordinate economic activities.

Variable tolls on roads

a. are politically unpopular because people do not like the idea of paying for a good that they used to consume without paying for it directly. b. rise when traffic volume increases to ensure the speed on the road is kept high. c. are an effective way of correcting the common resource problem on roads. d. All of the above are correct.