Question: when did nigeria change its currency from pounds to naira
[{'answer': '1 January 1973', 'provenance': [{'wikipedia_id': '178686', 'title': 'Nigerian naira', 'start_paragraph_id': 4, 'start_character': 28, 'end_paragraph_id': 4, 'end_character': 42, 'bleu_score': 1.0, 'section': 'Section::::History.\n'}]}, {'provenance': [{'wikipedia_id': '178686', 'title': 'Nigerian naira', 'start_paragraph_id': 4, 'start_character': 4, 'end_paragraph_id': 4, 'end_character': 364, 'bleu_score': 0.7839738459730551, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 9144066031345146050}, 'section': 'Section::::History.\n'}]}]