Suppose the parameters of the IS curve are ¯a = 0, ¯b = 0.5, ¯r = 3% and the real interest rate is initially R = 3%. (a) Is the economy in its long-term equilibrium? Explain. (b) Suppose the real interest rate falls to 2 percent; what happens to the short-run equilibrium, holding everything else constant? (c) What happens to the short-run equilibrium if ¯ag falls 3 percent, holding everything else constant? (d) What occurs if the marginal product of capital rises to 5 percent, holding everything else constant? What would cause this to happen?

The business cycle is the periodic but irregular up-and-down movement in economic activity, measured by fluctuations in real gross domestic product (gdp) and other macroeconomic variables. a business cycle is typically characterized by four phases—recession, recovery, growth, and decline—that repeat themselves over time. economists note, however, that complete business cycles vary in length. the duration of business cycles can be anywhere from about two to twelve years, with most cycles averaging six years in length. some business analysts use the business cycle model and terminology to study and explain fluctuations in business inventory and other individual elements of corporate operations. but the term "business cycle" is still primarily associated with larger (industry-wide, regional, national, or even international) business trends.