Explanation:

- 'A' alone can complete the work in 15 days: A earns Rs 6,500 for this work.

- Work rate of 'A': A’s daily rate is Rs 6,500 / 15 = Rs 433.33.

- With 'B', the work finishes in 12 days: So, the total amount remains Rs 6,500.

- Total earnings per day with 'A' and 'B': Rs 6,500 / 12 = Rs 541.67.

- Contribution of 'B' per day: Rs 541.67 - Rs 433.33 = Rs 108.34.

- 'B’s earnings for 12 days: Rs 108.34 × 12 = Rs 1,300.

- Correct Answer: Option 4, Rs 1,300.

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