Explanation:

- Let A = 8x, B = 9x

- B : C = 2 : 3 ? B = 2y, C = 3y

- C : D = 9 : 13 ? C = 9z, D = 13z

- Equate B from both: 9x = 2y ? y = (9x)/2

- Equate C from both: 3y = 9z ? y = 3z

- Substitute y from above: (9x)/2 = 3z ? z = (9x)/6

- Now express all in x:

- A = 8x

- B = 9x

- C = 3y = 3*(9x/2) = (27x)/2

- D = 13z = 13*((9x)/6) = (117x)/6

- The sum: 8x + 9x + (27x)/2 + (117x)/6 = 12000

- Taking LCM (6): (48x + 54x + 81x + 117x)/6 = 12000

- Sum: (48+54+81+117)x = 300x

- 300x / 6 = 12000 ? 50x = 12000 ? x = 240

- Now, B = 9x = Rs 2160; D = (117x)/6 = (117*240)/6 = Rs 4,680

- Difference: 4680 - 2160 = Rs 2,520

Option 3, Rs2,520 is correct.