Final answer:
The IS curve represents the relationship between output (Y) and the real interest rate (r) in a closed economy. The equation for the IS curve is Y = 2000. This equation shows the equilibrium level of output for different values of the real interest rate r.
Step-by-step explanation:
The IS curve represents the relationship between output (Y) and the real interest rate (r) in a closed economy. To derive the IS curve, we need to set aggregate expenditure (AE) equal to output. Using the given information:
AE = C + I
AE = (200+0.9(Y-T)) + 600
AE = 800 + 0.9Y - 0.3Y
AE = 800 + 0.6Y
Equating AE to output (Y):
Y = AE
Y = 800 + 0.6Y
Subtracting 0.6Y from both sides:
0.4Y = 800
Y = 2000
Thus, the IS curve is Y = 2000, which shows the equilibrium level of output for different values of the real interest rate r.