Help with this multiple choice fields and forces question

[scarlettjazz]

The question is here:

http://i1187.photobucket.com/albums/z393/scarlettjazz1/Fieldsandforces.png

The answer is B, but I can't figure out why. I get that the direction of the field is to the right, but I can't figure out why the strength is as it is.

Thanks!

[HiggsHunter]

The gravitational field strength is equal to the negative potential gradient of the gravitational field. From the plot, the potential gradient at point P is about -10 J/kg per 2m, or -5 J/kg per m. So the field strength at that point is 5 N/kg.

The direction of the potential gradient is to the left so, as you deduced correctly, the direction of the field is to the right.