May someone help me to understand this physics problem ? I was absent and don't understand how to do this.

Shown are two cases where three charges are placed in a row. Three students are Case A comparing the electric field that exerts a force on the middle charge in the diagrams. -3 mC +6 mC -3 mC Adrianna: "All three charges contribute by the principle of superposition. So the field is going to be greatest in case A since the contributions due to the O O O three charges will be greatest." X X Brandon: "I think it's a bogus question. The field at that point is undefined Case B because there is a charge there." -3 mc +3 mc -3 mC Catalina: "I don't think that's right. The field that exerts a force on the middle O O charge is the field due to the other two charges because a charge cannot feel it own field. Since those other two charges don't change, X X the field acting on the middle charge is the same in both cases." With which of these students do you agree