A 0.100 kg white ball moving with a velocity of 5 m/s 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 degree with respect to the positive x-axis and at a velocity 3.5 m/s. The blue ball moves at an angle of -35 degree and a velocity of 2.1 m/s. Determine what is the final y-momentum of the system?