int fee = 10; //You didn't say how much the fee started as.
for (int year = 0\1; i <= end; year++)
fee = fee * 1.04;
//At this point, use whatever cout you want, the fee is simply called fee, year is called year
Its a bit of a difficult task to guess why you gave up. But I would make a guess that you need to add the 4% to the existing fee, which will make the fee grow somewhat larger each year.
You could do that in two different ways.
Here it is shown in full: fee = fee + fee*.04;
There is also a more concise way of expressing it, by combining 100% + 4% into a single figure of 104%, like this: fee *= 1.04;
These both achieve the same result.