A 35-year-old otherwise healthy man presents to your suburban GP with a 3-day history of fever, productive cough with rusty sputum and pleuritic chest pain. He is a non-smoker. On examination, his temperature is 38.5°C, respiratory rate 20 breaths/min, blood pressure 122/76 mmHg and oxygen saturation 97% on room air. Chest auscultation reveals crackles in the right lower zone. You diagnose low-severity community-acquired pneumonia suitable for outpatient management. Which is the most appropriate empirical antibiotic regimen?