Question: when was the first motte and bailey castle built
[{'answer': '979', 'provenance': [{'wikipedia_id': '373601', 'title': 'Motte-and-bailey castle', 'start_paragraph_id': 22, 'start_character': 261, 'end_paragraph_id': 22, 'end_character': 264, 'bleu_score': 1.0, 'section': 'Section::::History.:Initial development, 10th and 11th centuries.\n'}]}, {'provenance': [{'wikipedia_id': '373601', 'title': 'Motte-and-bailey castle', 'start_paragraph_id': 22, 'start_character': 0, 'end_paragraph_id': 22, 'end_character': 979, 'bleu_score': 0.987691721403756, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 8359934441352034212}, 'section': 'Section::::History.:Initial development, 10th and 11th centuries.\n'}]}]