Question: who are the big 4 banks in australia
[{'answer': 'National Australia Bank', 'provenance': [{'wikipedia_id': '6947645', 'title': 'Big Four (banking)', 'start_paragraph_id': 10, 'start_character': 12, 'end_paragraph_id': 10, 'end_character': 35, 'bleu_score': 1.0, 'section': 'Section::::Australia/New Zealand.\n'}]}, {'answer': 'Commonwealth Bank', 'provenance': [{'wikipedia_id': '6947645', 'title': 'Big Four (banking)', 'start_paragraph_id': 14, 'start_character': 250, 'end_paragraph_id': 14, 'end_character': 267, 'bleu_score': 1.0, 'section': 'Section::::Australia/New Zealand.\n'}]}, {'answer': 'Westpac', 'provenance': [{'wikipedia_id': '6947645', 'title': 'Big Four (banking)', 'start_paragraph_id': 14, 'start_character': 210, 'end_paragraph_id': 14, 'end_character': 217, 'bleu_score': 1.0, 'section': 'Section::::Australia/New Zealand.\n'}]}, {'answer': 'Australia and New Zealand Banking Group'}]