What Is the Most Common Cause of Upper Gastrointestinal Bleeding

Mr. Santos, a 65-year-old Male, Presents to the Emergency Department with Complaints of Black, Tarry Stools for the Past 3 Days. He Reports Feeling Weak and Lightheaded. on Physical Examination, His Blood Pressure Is 90/60 Mmhg, Heart Rate Is 110 Bpm and He Appears Pale