Question: when did rolls royce start making jet engines
[{'answer': '1940', 'provenance': [{'wikipedia_id': '5455080', 'title': 'Rolls-Royce Limited', 'start_paragraph_id': 1, 'start_character': 432, 'end_paragraph_id': 1, 'end_character': 436, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]