Work on a proton/Electic Potential

[sdoyle1]

Homework Statement

Imagine that a proton is held on the end of an insulated rod. How much external work is needed to move the proton from a point with a potential of 95 V to a point where it is -54V?
Express your answer in Joules, watch out for the sign of the answer.

Homework Equations

The Attempt at a Solution

I thought that you could use U=qV but it's not working- I also don't know what the point charge (q) would be. I chose this equation because you can relate the change in potential to work (U=-W)... Guidance would be great!

 

[sdoyle1]

Nevermind, I figured it out.. :)