In the short run, the price at which a firm's total revenues equal its total costs is

Which of the following is an example of using the scientific method with a natural experiment?

a. measuring how long it takes a marble to fall from a ten story building b. comparing plant growth with and without a soil additive c. tracking the price of oil when a war in the Middle East interrupts the flow of crude oil d. observing the reaction when two chemicals are mixed together

________ are forces that cause a reduction in a firm's average cost as the scale operation increases in the long run. ________ are forces that cause a firm's average cost to increase as the scale of operation increases in the long run

a. Diseconomies of scale; economies of scale. b. Economies of scale; diseconomies of scale. c. Increasing returns to a factor; decreasing returns to a factor d. Decreasing returns to a factor; increasing returns to a factor