A 28 year old man with no known medical history presents to the emergency department with fever, productive cough with rusty sputum, and pleuritic chest pain for 3 days. Temperature is 102.4 degrees Fahrenheit, respiratory rate 28 per min, blood pressure 118 over 70 mm Hg, and oxygen saturation 93 percent on room air. Lung exam reveals right lower lobe crackles. Chest radiograph confirms a right lower lobe consolidation. He has no recent antibiotic use and no comorbidities. What is the most appropriate empiric outpatient antibiotic regimen?