Question: when did zambia win the african cup of nations
[{'answer': '12 February 2012', 'provenance': [{'wikipedia_id': '34653974', 'title': '2012 Africa Cup of Nations Final', 'start_paragraph_id': 1, 'start_character': 77, 'end_paragraph_id': 1, 'end_character': 93, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]