Could I kindly suggest that you try to narrow down the problem ? Please don't take this the wrong way - I'm really trying to help, but I've had trouble following all the code, which wasn't necessarily relevant to the question. Shorter code is likely to bring you much more replies.
In your case, if you're having a linking problem (one class can't use the other), can you please try post a version with shorter classes ? You could probably reproduce the error message, even if each class has just 3-4 lines of code (with some "hello world" method instead of the complicated currency calculations)...
It will also help if you quote the exact error message, and which line of code it's referring to.
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