Explanation:

- Ram spends 40% of his income on food and 20% on room rent.

- He saves 25% of what's left after these expenses.

- The remaining amount after savings is invested in mutual funds and life insurance at a 3:2 ratio.

- The difference between mutual fund and life insurance investments is Rs. 1,800.

To find his monthly income (\(x\)):

1. Total expenses on food and rent: 60% of \(x\) (as 40% + 20%).

2. Remaining after food and rent: 40% of \(x\).

3. Saving from remaining: Saves 25% of 40%, so 10% of \(x\).

4. Left for investment: 30% of \(x\), invested in a 3:2 ratio.

- Difference between investments:

$$

\left(\frac{3}{5} \times 0.3x\right) - \left(\frac{2}{5} \times 0.3x\right) = 1800

$$

- Solving gives:

$$

\left(0.18x - 0.12x\right) = 1800

$$

$$

0.06x = 1800 \Rightarrow x = 30000

$$

- Option: 4 - Rs. 30,000 is correct.

.