3. (15 percent) Desired consumption and investment are Ca = 360 -200r + 0.10Y 7 = 120 - 400r As usual, Y' is output and / is the real interest rate. Government purchases G are 120. a. Find an equation relating desired national saving S" to > and Y. b. What value of the real interest rate clears the goods market when Y= 600? Use both forms of the goods market equilibrium condition. What value of the real interest rate clears the goods market when Y= 640? What if Y= 560? What if Y= 680? c. Graph the IS curve