Jesus, matrix problems are challenging af!

Too complicate, the answer should be more simple.

Agreed!

Did you notice this in the description:

If p% is the rate for a year the rate for a day is p divided by 36000 since banks consider that there are 360 days in a year.

And this is not clear from the description - should be added to it.

Thanks!

Input parameter unsigned long, in that way will work. See the issue raised by masterridley.