A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of understanding income. It is a general statement that does not need other sentences for context. It sets up the theme of managing finances. Why other lines are not chosen? Paragraph 2 starts with 'Begin', which is a command and does not stand alone. Paragraph 3 uses 'After', which shows a sequence and needs prior context. Paragraph 4 starts with 'Once', which also needs earlier information to make sense.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the process of managing finances. It shows the importance of reviewing expenses, which is a final step in financial planning.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): This pair connects because after knowing your income, you need to track your expenses. This shows a logical order of steps in managing finances.
• Pair 2 (Paragraph 2 → Paragraph 3): This pair links because after tracking expenses, you can see your income and expenses clearly. This leads to setting savings goals, showing a clear logical order.
• Pair 3 (Paragraph 3 → Paragraph 4): This pair connects because after setting savings goals, you need to review your expenses regularly. This shows a logical order of actions in financial management.