Explanation:

- Initial capital: On 1st April 2018, the capital was 2,00,000.

- Additional capital: He introduced 1,00,000 on 1st October 2018.

- Interest rate: Interest on capital is calculated at 6% per annum.

Interest Calculation:

- For the initial capital (2,00,000):

- Period: 1st April 2018 - 31st March 2019 = 12 months

- Interest = 2,00,000 × 6% = 12,000

- For the additional capital (1,00,000):

- Period: 1st October 2018 - 31st March 2019 = 6 months

- Interest = 1,00,000 × 6% × (6/12) = 3,000

- Total interest = 12,000 + 3,000 = 15,000

Correct Answer as Explanation:

- Option 1: 9,000 is too low as it doesn't cover both capitals.

- Option 2: 18,000 is incorrect as the calculation shows 15,000.

- Option 3: 10,500 is not matching with the calculated total.

- Option 4: 15,000 is the correct answer, matching the calculation.

Based on the calculation, "".