Q. A 4-year-old girl is brought to the pediatric clinic by her parents with a 3-day history of fever, productive cough, and reduced appetite. The parents deny any recent travel or contact with sick people. The child is up-to-date with her immunizations. On physical examination, the girl appears mildly distressed. Her temperature is 39.0°C (102.2°F). Auscultation of the lungs reveals localized crackles in the right lower lung zone. A chest x-ray confirms a consolidation in the right lower lobe. What is the most appropriate first-line treatment for this patient’s condition?