Fixed.

Which language?

Fixed, Thanks.

You can do the change of percentage when you want... but calculate with the correct one at the end of the month. Once more, description says:

Calculations are processed at the end of each considered month

My solution is not maybe the best but if you have time take a look at it:-)

Description:

percent of loss increases by 0.5 percent at the end of every two months

• So to make your calculations at the end of month 1 you use the initial loss
• .............................at the end of month 2 you use the initial loss increased by 0.5 percent

With the example given in the description
nbMonths(2000, 8000, 1000, 1.5) should return [6, 766]
you get for "months", "percentLossByMonth", "available" (rounded):

1   1.5   -4910
2   2.0   -3792
3   2.0   -2676
4   2.5   -1534
5   2.5   -396
6   3.0   766

The thing to understand is: at each step you use the correct percentLossByMonth before doing your calculations. Is that clearer?