Change in electric potential between 2 parallel plates

[Runaway]

Homework Statement

A proton is released from rest in a uniform electric field of mag. 90000 V/m directed along the positive x axis. the proton undergoes a displacement of .2m in the direction of the electric field. Find the change in electric potential.

Homework Equations

no idea

The Attempt at a Solution

I have no idea where to start, an equation would be nice but I can't find anything in the book about electric potential in a uniform electric field.
First I tried 90000V/m * .2m but that didn't work, then I tried using V= kq/r, V=k * <charge of a proton> / .2m, but that didn't work either.

 

[JaWiB]

Electric potential difference is minus the work done by the electric field divided by the charge. So the question is, what work would the electric field do on this charge over that distance?

Any physics textbook worth its salt should explain this, so I suggest looking harder or getting a new book.