Question: Finland won the first Eurovision Dance Contest in 2007, in 2008, Finland were represented by singer and actress Maria Lund, and dancer Mikko Ahti, danced a Tango,a Tango is a partner dance, that originated in the 1880s, along which location, the natural border between Argentina and Uruguay?
{'answer': 'River Plata', 'supporting_facts': [['Finland in the Eurovision Dance Contest', 6], ['Tango', 0]]}