Question: when was penn state added to the big ten
[{'answer': '1990', 'provenance': [{'wikipedia_id': '78358', 'title': 'Big Ten Conference', 'start_paragraph_id': 4, 'start_character': 346, 'end_paragraph_id': 4, 'end_character': 350, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]