Solution:
A) The potential energy contained in a proton that is positively charged from 5.0v potential location to 7.5v potential location will increase. This is due to the fact that energy is expended on the proton within an electric field to be able to move it from its original state to a higher potential location.
B) If an electron moves from a location with 7.5v potential to a location with 5.0v potential, its potential energy would decrease. This is because as it loses charges, it also loses some of its potential energy, all of which brings it to a lower potential location.