A 20-year-old man is referred for evaluation of hypertension. He states he has never had any health problem. On examination, he appears in no apparent distress. His height is 175 cm, and his weight is 70 kg. Blood pressure is 162/80 mmHg in the upper extremities and Ul5/77 mmHg in the lower extremities. There is no jugular venous distension or pitting deem of the legs. The lungs are clear to auscultation. A systolic murmur is appreciated at the base of the heart and particularly intense at the back. Femoral pulses are weaker than radial pulses The ECG shows signs of left ventricular hypertrophy. Chest x ray shows notching of the inferior margins of the ribs. Which of the following is most likely diagnosis?