Giả sử không có Chính phủ và ngoại thương nếu tiêu dùng tự định là 30, đầu tư là 40, MPS = 0,1. Mức sản lượng cân bằng là:A. Khoảng 77B. 430C. 700D. 400

1. Break Down the Problem

We need to find the equilibrium output level (Y) in an economy without government and foreign trade, using the following data:

• Autonomous consumption (C) = 30
• Investment (I) = 40
• Marginal Propensity to Save (MPS) = 0.1

2. Relevant Concepts

To find the equilibrium output, we need to use the formula relating consumption and saving:

• MPS = 1 - MPC, where MPC is the Marginal Propensity to Consume.
• Total expenditure (TE) = consumption + investment: $TE = C + I$

The output level is reached when total expenditure equals output (Y): $Y = TE$

3. Analysis and Detail

1. Calculate the Marginal Propensity to Consume (MPC): $MPC = 1 - MPS = 1 - 0.1 = 0.9$

2. Calculate consumption as a function of income (Y): Since consumption is dependent on income, it can be represented as: $C = C_0 + MPC \cdot Y$ Where $C_0$ is the autonomous consumption (30).

3. Substitute known values into the consumption equation: $C = 30 + 0.9Y$

4. Set up the equilibrium condition: $Y = C + I$ Substitute in the known values: $Y = (30 + 0.9Y) + 40$

5. Simplify and solve for Y: $Y = 70 + 0.9Y$ $Y - 0.9Y = 70$ $0.1Y = 70$ $Y = \frac{70}{0.1} = 700$

4. Verify and Summarize

We have calculated the equilibrium output level as 700. Upon verifying the calculations, the equilibrium condition holds true.

Final Answer

The equilibrium output level is 700 (Option C).