Question: a cost that has already been incurred and cannot be changed is called a(n)
[{'answer': 'sunk cost', 'provenance': [{'wikipedia_id': '102913', 'title': 'Sunk cost', 'start_paragraph_id': 1, 'start_character': 45, 'end_paragraph_id': 1, 'end_character': 54, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '102913', 'title': 'Sunk cost', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 154, 'bleu_score': 0.7718431441428121, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 13441475243570277605}, 'section': 'Section::::Abstract.'}]}]