A sum of money earns a simple interest at 7.25% per annum for the first eight years, at 8.5% for the next six years, and at 6.5% for the final four years. If the total interest earned during these eighteen years was ₹35, 100, what was the original sum invested (in ₹)?

A

25,800

B

25,500

C

26,400

D

26,000