A 3C positive charge is released from rest at point P and is found to gain 24J of kinetic energy when it reaches point Q.
a. (i) Taking the charge movement as the positive direction P→Q, calculate the work done by the electric field per unit charge.
b. (ii) Hence find the potential difference VQP between points Q and P, including its sign.
c. (iii) If an external agent now slowly moves the same 3C charge from Q back to P, how much work must the agent do? State whether this work is positive or negative and give a reason.