A 0.100–kilogram white ball moving with a velocity of 5 meters/second along the positive x–axis hits a stationary blue ball of the same mass. Energy is not necessarily conserved, but momentum is. After the collision, the white ball moves off at an angle of 20° with respect to the positive x–axis and at a velocity 3.5 meters/second. The blue ball moves at an angle of –35° and a velocity of 2.1 meters/second. What is the final y–momentum of the system?