The poll on the left is based on a picture from Serway. I've changed it a bit, and not just so the Serway Lawyers don't come after me -- I've made the question more conceptual than mathematical. Go ahead and vote. I'll post results next weekend, along with a discussion of the change I made and why I made it.
FYI, my AP class has just begun studying electric fields due to point charges. This is their first homework problem, with the request for a justification of the answer, of course.