Find the interest produced in 4 years by a capital of Q10,000 lent at 9% with annual simple interest.

Solution:
1. Given:
- Principal (P): Q10,000
- Rate (R): 9%
- Time (T): 4 years

2. Use the formula for simple interest:
- Simple Interest (SI) = \frac{P \times R \times T}{100}

3. Substitute the given values into the formula:
- SI = \frac{10000 \times 9 \times 4}{100}

4. Calculate the simple interest:
- SI = \frac{360000}{100}
- SI = Q3,600

The simple interest earned is Q3,600.