REF: The IS model. A change in generates a movement along the IS curve; an increase in increases at any given value of R. An increase in shifts the IS curve. Select one: a. R,r, output, aggregate demand, out b. r, R, potential output, aggregate demand, in c. marginal productivity of capital, r, output, investment, out d. R,r, potential output, aggregate demand, to the left e. R,r, potential output, aggregate investment, to the right.