Question: who has the power to set up a postal system
[{'answer': 'Congress', 'provenance': [{'wikipedia_id': '50591', 'title': 'United States Postal Service', 'start_paragraph_id': 2, 'start_character': 64, 'end_paragraph_id': 2, 'end_character': 72, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]