Explanation:

- A and B start a business with Rs. 4000 and Rs. 5500, respectively.

- After 6 months, A reduces his investment to Rs. 3000, and B to Rs. 4000.

- C joins with an investment of Rs. 4x.

- The business runs for a total of 15 months (1 year and 3 months).

Calculation of ratios:

- A's share for 6 months = Rs. 4000 for 6 months = 24000

- A's share for the next 9 months = Rs. 3000 for 9 months = 27000

- Total A = 24000 + 27000 = 51000

- B's share for 6 months = Rs. 5500 for 6 months = 33000

- B's share for 9 months = Rs. 4000 for 9 months = 36000

- Total B = 33000 + 36000 = 69000

- C's share for 9 months (as he joined after 6 months) = 9 * 4x = 36x

Profit share ratios:

- Total Profit = Rs. 12250

- C's share = Rs. 2250

- (36x / (51000 + 69000 + 36x)) * 12250 = 2250

- Solving yields x = 750, so C’s investment = 4x = 3000

- Correct Answer: Option 4 - Rs. 3000

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