Explanation:

To determine the additional interest earned through compound interest, let's break down the problem:

- Simple Interest (SI): Rs. 400 for 2 years at 5% per annum means the sum (Principal) is Rs. 400/0.10 = Rs. 4000.

- Compound Interest (CI) formula considering yearly compounding:

- CI = Principal \((1 + \frac{rate}{100})^n - Principal\)

- CI = Rs. 4000 \((1 + \frac{5}{100})^2 - Rs. 4000\)

- CI = Rs. 4000 \((1.05)^2 - Rs. 4000\)

- CI = Rs. 4000 \((1.1025) - Rs. 4000\)

- CI = Rs. 4410 - Rs. 4000 = Rs. 410

- Additional Interest: CI - SI = Rs. 410 - Rs. 400 = Rs. 10

- Correct Answer: Option 3, 10

- Therefore, the additional interest earned is Rs. 10.