Explanation:

To solve this problem, let's consider the facts and calculations necessary:

- Principle Information:

- The sum amounts to Rs12,000 in 5 years and Rs18,000 in 8 years using simple interest.

- Simple Interest Formula:

- Simple Interest (SI) = Principal (P) × Rate (R) × Time (T) / 100

- Interest Over 3 Years:

- Difference in amount from year 5 to year 8 = Rs18,000 - Rs12,000 = Rs6,000

- This Rs6,000 is the interest for 3 years.

- Calculate Annual Interest:

- Annual interest = Rs6,000 / 3 = Rs2,000

- Determine Principal and Rate:

- Using the year 5 amount: Rs12,000 = P + 5 × (2,000)

- Principal (P) = Rs12,000 - Rs10,000 = Rs2,000

- Calculate Rate:

- Since Rs2,000 earns Rs2,000 annually, the rate is:

- Rate = (Annual Interest / Principal) × 100 = (2,000 / 2,000) × 100 = 100%

- Correct Option:

- Option: 3, 100%