A 3.20 x 10-19 C particle moves through a region of space where an electric field of magnitude 27.3 N/C points in the negative x direction, and a magnetic field of magnitude 0.0258 T points in the positive z direction. If the net force acting on the particle is 7.82 x 10-18 N in the negative x direction, find the magnitude and direction of the particle's velocity.