Option 3: 900 -> At equilibrium Y = 1000, first calculate savings: S = -100 + 0.2(1000) = -100 + 200 = 100. Since Y = C + S in a two-sector economy, Consumption C = Y - S = 1000 - 100 = 900. Alternatively, from the saving function with MPS = 0.2, we get MPC = 0.8 and autonomous consumption = 100, so C = 100 + 0.8Y = 100 + 0.8(1000) = 900 -> correct