Rohan borrows a certain sum at simple interest. Rate of interest is 3 percent per annum for first 3 years, 4 percent per annum for next 5 years and 6 percent per annum for next 7 years. If he paid Rs. 2485 as interest, then what is the sum borrowed?

A

Rs. 2500

B

Rs. 3500

C

Rs. 4000

D

Rs. 3600