Explanation:

- Let's assume the initial salary is \( x \).

- After the first increment of \( p\% \), the salary becomes \( x + \frac{px}{100} = x(1 + \frac{p}{100}) \).

- The second increment is \( 4p\% \). Hence, the salary becomes:

$$ x(1 + \frac{p}{100}) \times (1 + \frac{4p}{100}) $$

- This final salary is given to be 2.5 times the initial salary, so:

$$ x(1 + \frac{p}{100})(1 + \frac{4p}{100}) = 2.5x $$

- By simplifying and solving the equation, you find \( p \) such that \( 1.5 + \frac{5p}{100} + \frac{4p^2}{10000} = 1.5 \).

- Option 1: 10%

- If \( p = 10\% \), second increment is \( 40\% \).

- Final salary = \( x \times 1.1 \times 1.4 = 1.54x \); not equal to 2.5x.

- Option 2: 25% ()

- If \( p = 25\% \), second increment is \( 100\% \).

- Final salary = \( x \times 1.25 \times 2 = 2.5x \).

- Option 3: 50%

- If \( p = 50\% \), second increment is \( 200\% \).

- Final salary = \( x \times 1.5 \times 3 = 4.5x \); overshoots 2.5x.

- Option 4: 12%

- If \( p = 12\% \), second increment is \( 48\% \).

- Final salary = \( x \times 1.12 \times 1.48 \approx 1.66x \); not equal to 2.5x.