Question: when did the google pixel book come out
[{'answer': 'February 21 , 2013', 'provenance': [{'wikipedia_id': '38597392', 'title': 'Chromebook Pixel', 'start_paragraph_id': 7, 'start_character': 74, 'end_paragraph_id': 7, 'end_character': 92, 'bleu_score': 1.0, 'section': 'Section::::Technology.\n'}]}]