834 3% 15 months simple interest

If it is 3% for a year then

834 x 3/100 = 25.02 which is for 12 months.

The next three months is (25.02/12) x3 = 6.25 for 3 months

So for 15 months 25.02+6.25 = 31.45

But if it is 3% monthly then

25.02 x 15 = 375.30