A sum of Rs. 20000 is invested for three years at compound interest. The rate of interest for first year is 20 percent per annum, for second year it is 15 percent per annum and for third years it is 10 percent per annum. Find the interest for the third year.

A

Rs. 2760

B

Rs. 2620

C

Rs. 2190

D

Rs. 2340