Question: what commodity formed the economic backbone of bengal in the eighteenth century
[{'answer': 'cotton cloth', 'provenance': [{'wikipedia_id': '21670823', 'title': 'Economy of India under Company rule', 'start_paragraph_id': 4, 'start_character': 241, 'end_paragraph_id': 4, 'end_character': 253, 'bleu_score': 1.0, 'section': 'Section::::Economic impact.\n'}]}, {'provenance': [{'wikipedia_id': '21670823', 'title': 'Economy of India under Company rule', 'start_paragraph_id': 4, 'start_character': 0, 'end_paragraph_id': 4, 'end_character': 605, 'bleu_score': 0.980097014099621, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 6267231839725042634}, 'section': 'Section::::Economic impact.\n'}]}]