Question: how many sons did jacob have with rachel
[{'answer': 'two', 'provenance': [{'wikipedia_id': '20314501', 'title': 'Rachel', 'start_paragraph_id': 1, 'start_character': 80, 'end_paragraph_id': 1, 'end_character': 83, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]