Question: where is the ncaa national football championship played
[{'answer': 'Mercedes - Benz Stadium', 'provenance': [{'wikipedia_id': '48966894', 'title': '2018 College Football Playoff National Championship', 'start_paragraph_id': 20, 'start_character': 227, 'end_paragraph_id': 20, 'end_character': 250, 'bleu_score': 1.0, 'section': 'Section::::Broadcasting.\n'}]}]