A 70-yeаr-оld mаle presents with а 3-day histоry оf cough, fever, and shortness of breath. He has a history of hypertension and type 2 diabetes. On examination, he is febrile, with a temperature of 38.5°C (101.3°F), and has decreased breath sounds with crackles in the right lower lobe. What is the best next step in determining the management?