Explanation:

- The original distribution should have been in the ratio 3:4:5.

- The erroneous distribution happened in the ratio 9:4:7.

- We know that B received Rs. 60 less due to the error.

- In the original distribution, B would have received 4 parts.

- In the erroneous distribution, B receives 4 parts as well.

- However, the relative proportions to the total amount are different.

- Formula: Assume total amount = x.

- Original share for B = (4/12) * x = (1/3) * x.

- Erroneous share for B = (4/20) * x = (1/5) * x.

- Difference = (1/3)x - (1/5)x = (5x/15) - (3x/15) = (2x/15).

- According to the problem, this difference is Rs. 60.

- So, 2x/15 = 60.

- Solving gives x = 450.

- The total amount is Rs. 450.

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