Answer:
the electric field direction should be in positive y axis
Explanation:
Lets assume that charge on particle is positive and it isequal to +q
First calculate the magnetic force on it
for direction
use Right Hand Rule which will give the direction and by using his the direction will come towards negative y axis.
As given in the question that charge particle does not change their velocity so we need to apply electric field in such a way that electric force direction should be opposite to the magnectic field.
and magnitude should be same as magnectic force and also direcion of electric force depend on the direction of elecric field when charge is positive because electric force
Hence the electric field direction should be in positive y axis