A 58-year-old woman presents with fever, productive cough and pleuritic chest pain. She is tachypnoeic at 26 breaths/min, oxygen saturation 94% on room air, blood pressure 120/70 mmHg and heart rate 104 beats/min. Chest examination reveals crackles over the right lower zone; chest X-ray confirms right lower lobe consolidation. She has no major comorbidities and is suitable for outpatient management. Which antibiotic regimen is most appropriate empiric therapy?