Question: how many episodes are there in last man on earth season 4
[{'answer': '18', 'provenance': [{'wikipedia_id': '45554955', 'title': 'List of The Last Man on Earth episodes', 'start_paragraph_id': 2, 'start_character': 88, 'end_paragraph_id': 2, 'end_character': 90, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]