Question: what is default extension of file in excel 2010
[{'answer': '. xlsx', 'provenance': [{'wikipedia_id': '7427473', 'title': 'List of Microsoft Office filename extensions', 'start_paragraph_id': 20, 'start_character': 57, 'end_paragraph_id': 20, 'end_character': 62, 'bleu_score': 1.0, 'section': 'Section::::Excel.\n'}]}]