Question: when did the currency of botswana came in circulation
[{'answer': '1976', 'provenance': [{'wikipedia_id': '544898', 'title': 'Botswana pula', 'start_paragraph_id': 4, 'start_character': 27, 'end_paragraph_id': 4, 'end_character': 31, 'bleu_score': 1.0, 'section': 'Section::::History.\n'}]}]