Question: when did the first mustang fastback come out
[{'answer': 'August 1964', 'provenance': [{'wikipedia_id': '15788292', 'title': 'Ford Mustang (first generation)', 'start_paragraph_id': 2, 'start_character': 117, 'end_paragraph_id': 2, 'end_character': 128, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '15788292', 'title': 'Ford Mustang (first generation)', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 257, 'bleu_score': 0.8698334915282521, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 591203080425609429}, 'section': 'Section::::Abstract.'}]}]