Answer
The speed of the particle with charge $+q_1$ will increase.
The speed of the particle with charge $+q_2$ will decrease.
The speed of the particle with charge $-q_3$ will increase.
The speed of the neutron will remain the same.
Work Step by Step
In part (a), we found that the direction of the electric field points from plate A to plate B.
We can write the equation for the force on a charge due to an electric field:
$F = q~E$
The force on a positive charge will be directed from plate A toward plate B.
The force on a negative charge will be directed from plate B toward plate A.
Therefore:
The speed of the particle with charge $+q_1$ will increase.
The speed of the particle with charge $+q_2$ will decrease.
The speed of the particle with charge $-q_3$ will increase.
The speed of the neutron will remain the same since it does not have a charge.
