A proton, with a velocity of 3.45 x 10^5 m/s to the north, experiences both a magnetic force and electric force, working in the same direction. The net force causes the proton to accelerate at 2.86 x 10^14 m/s^2 to the east. If the electric field has a strength of 2.00 x 10^6 N/C, what is the magnitude and direction of the magentic field?