To find the equilibrium national income (Y), we can use the basic macroeconomic identity, which states that in equilibrium, aggregate demand (AD) equals aggregate supply (Y).
The aggregate demand can be expressed as:
\[
AD = C + I + G + (X - M)
\]
Where:
- \( C \) is consumption,
- \( I \) is investment,
- \( G \) is government spending,
- \( X \) is exports,
- \( M \) is imports.
### Step 1: Express C and M in terms of Y
1. **Consumption