Answer
Please see the work below.
Work Step by Step
(a) We know that according to the right hand rule, if the direction of the velocity of the positive charged particles is in the positive z-direction, and the direction of the magnetic field is in the positive y-direction, then the direction of the electric field is in the positive x-direction.
(b) We know that according to the right hand rule, if the direction of the velocity of the negative charged particles is in the positive z-direction and the direction of the magnetic field is in the positive y-direction, then the direction of the electric field is in the positive x-direction.