A proton moves from point \(A\) to point \(B\) under the influence of an electrostatic field in which the potential difference between A and B is negative.

(a) If your system includes both the proton and the particles generating the electrostatic field, does the system's electric potential energy increase, decrease, or remain the same?

(b) Does the proton's kinetic energy increase, decrease, or remain the same?

(c) How would the answers in parts \(a\) and \(b\) change if your system included only the proton?