ok a massive problem for me... !
done the code fine, but I keep failing the test where an empty array is handed to me, and then I cant coerce nil into integer. Thats fine.
I try every possible solution, break, exit, return, if statements when arr.empty? but none seem to work. Help?

I see your point, but 2 percent is not really 2.
2 percent is actually written as 0.02..
so you need to divide 2 by 100 to get 0.02
as a result you need to do the following
interest per day in decimal = (360 * 100) = 36000