Question: when did the vat rate change from 17.5 to 20
[{'answer': '4 January 2011', 'provenance': [{'wikipedia_id': '34027706', 'title': 'Value-added tax in the United Kingdom', 'start_paragraph_id': 2, 'start_character': 292, 'end_paragraph_id': 2, 'end_character': 306, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '34027706', 'title': 'Value-added tax in the United Kingdom', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 509, 'bleu_score': 0.977897140678983, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 17620442725976018818}, 'section': 'Section::::Abstract.'}]}]