A sum is divided among A,B,C and D such that the ratio of the shares of A and B is 3:5, that of B and C is 2:3 and that of C and D is 5:7. If the difference between the shares of C and A is Rs. 5580 , then the sum (in Rs.) of the shares of B and D is:

First, combine the ratios to get A:B:C:D = 6:10:15:21. Let the shares be 6k, 10k, 15k, 21k. Given C - A = 15k - 6k = 9k = 5580, so k = 620. Therefore B + D = 10k + 21k = 31k = 31 × 620 = 19220. Option A (18840) would result from incorrect ratio combination, while Option D (17980) uses an arithmetic error in the final step.