its a ques of maths..not of sst siso but i have an ans..hope it helps(^.^)
Solution :
Case 1: For the first two years <br>
<br>
<br> Case 2: For the remaining time period <br>
months <br>
<br>
. <br>
Total amount that Ravi has to pay =15,000 + 4500 + 400 = Rs 23,500