Question: what is the chemical formula of epsom salt
[{'answer': 'MgSO 7H O'}, {'provenance': [{'wikipedia_id': '246267', 'title': 'Magnesium sulfate', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 322, 'bleu_score': 0.736196275198539, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 5558880413137322757}, 'section': 'Section::::Abstract.'}]}]