C = 40 + 0.8Y lg = Tg = 40 X = X = 20 M = M = 30 (Advanced analysis) The equations give information for a private open economy. The letters Y, C, lg, X, and M stand for GDP, consumption, gross investment, exports, and imports, respectively. Figures are in billions of dollars. The equilibrium GDP (=Y) in the eocnomy is