Prime

Prime is appearing as a corpse at Dot's Diner at Jury Street Metro Station, but only when you answer correctly to the 3 terminals in the Museum of technology. The three terminals are recognizable by the #001 #002 and #003 option at the bottom of the options when you enter terminal. From the outside, they look like any other computer terminal on the wall. First terminal will have #000 for option, and when you past that, it'll change to #001 so you could start this kind of a mini game. The key here are prime numbers. After you answer all 3 terminals across the museum of technology, you will be awarded with a key to a safe in the museum, and will be told that Prime will wait you at the Dot's Dinner at Jury Street Metro Station. When you get there, you'll find the sweet Xuanlong Assault Rifle in his corpse.