Question: when did pennies stop being made of copper
[{'answer': '1982', 'provenance': [{'wikipedia_id': '164092', 'title': 'Penny (United States coin)', 'start_paragraph_id': 8, 'start_character': 38, 'end_paragraph_id': 8, 'end_character': 42, 'bleu_score': 1.0, 'section': 'Section::::History of composition.\n'}]}]