Answer:
Down.
Step-by-step explanation:
In the given question, the charged particle is moving towards the east direction. Suppose east direction towards the positive x-axis.
And the magnetic field directed towards to the north direction. Suppose north direction towards the positive y-axis.
Therefore force of magnetic field can be calculate by the formula,
Therefore force of the magnetic field is in positive z-axis means in an upward direction.
Now the force on the electric field must be in the opposite direction means it is in a downward direction.