A 94 kg physics student is wearing a 3 kg jacket. He is stranded in the middle of a frictionless frozen pond. Since there is no friction, he cannot walk off the pond since his shoes can't grip the ice. Since he cannot escape the ice, surely he is doomed to freeze to death. Luckily, since the student is in physics class, he knows conservation of momentum. He takes off his jacket and throws it east with a velocity of 15 m/s.

What is the magnitude of the student's velocity after throwing the jacket?