Explanation:

- Akshay invested an amount at a simple interest rate for 4 years.

- If the interest rate increased by 5%, there would be an additional Rs. 1500 earned.

- The difference in interest when the rate increases by 5% over 4 years can be expressed as:

$$ \text{Principal} \times \frac{5}{100} \times 4 = 1500 $$

- Simplifying the equation:

$$ \text{Principal} \times \frac{20}{100} = 1500 $$

$$ \text{Principal} \times 0.2 = 1500 $$

- Hence, the principal or the amount borrowed:

$$ \text{Principal} = \frac{1500}{0.2} = 7500 $$

- Correct Option: 2, Rs. 7,500