Hi Niranjan

The calculation is very simple

2500*4%=100 and divide it by 12

100/12=8.3 is month interest as of 2500

8.3*9=75 interest for 9 months

1500*4%=60 and divide it by 12

60/12=5 is month interest as of 1500

5*3=15 interest is for 3 months

The total interest payable at the end of the year is 75+15=90

Hope this information is helpful.