This is highly inefficient -> O(n^2) if the 2 arrays are of equal length. Improve it.

Why would the following : 25,25,25,25,25,100 expect a NO? I have dictionary for the "cash register" and I have enough "bills" to cover a 75$ cash return for the person in line when I come at he 100. Can someone explain this one to me ?

All my code is working. Although, it's too slow (took more than 6s)
What can I do to speed my code while using static methods/class

Should have random test for any kind of currency

Modified code to
TimeSpan time = TimeSpan.FromSeconds(seconds);
string str = time .ToString(@"hh:mm:ss");
Expected: "03:59:59"
But was: "99:59:59"
for seconds =359999
It does not make sense

I don't understand what's going on
Expected string length 10 but was 8. Strings differ at index 0.
Expected: "1.00:00:00"
But was: "24:00:00"

Convert.ToString( TimeSpan.FromSeconds( numOfSeconds ) )
The format does not stick to its premise. Why is it 1.00 instead of 24:00:00 ?

Can someone help me please !

Could it be possible to have this kata in C# too ?