Question: how many books are in stephen king's dark tower
[{'answer': 'eight', 'provenance': [{'wikipedia_id': '782607', 'title': 'The Dark Tower (series)', 'start_paragraph_id': 1, 'start_character': 30, 'end_paragraph_id': 1, 'end_character': 35, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '782607', 'title': 'The Dark Tower (series)', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 461, 'bleu_score': 0.576440682567076, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 13484897689495109384}, 'section': 'Section::::Abstract.'}]}]