A 35-year-old otherwise healthy man presents with a 3-day history of fever, pleuritic chest pain and productive cough with yellow sputum. He is febrile at 38.2 °C, respiratory rate 22 breaths/min, oxygen saturation 96% on room air and has left lower lobe crackles on examination. He is haemodynamically stable and suitable for outpatient treatment. What is the most appropriate empiric oral antibiotic regimen?