Farkas Lemma and its importance in the context of arbitrage theory (Finance)

Good morning everybody,

I have an oral exam soon and the question "Explain Farkas Lemma and its importance in the context of arbitrage theory" is a probable question which will come up...

As I missed that lecture, and the notes are not self-explanatory....does somebody have a suggestion what would be an appropriate answer....?

As it's strictly oral exam, no proof is required or further technicalities. What is the concept behind Farkas Lemma? I was not able to find a conceptual explanation of Farkas Lemma in the literature...!!! And what is its significance in the context of arbitrage theory...

Thank you for any insights, suggestions, links etc..!