A particle carrying charge \(+q\) is located on the \(x\) axis at \(x=+d\). A particle carrying charge \(-3 q\) is located on the \(x\) axis at \(x=-7 d\).

(a) With zero potential at infinity, at what locations on the \(x\) axis is the electrostatic potential zero?

(b) At what locations on the \(y\) axis is the potential zero?

(c) Answer the questions of parts \(a\) and \(b\) for the case where the object at \(x=-7 d\) carries charge \(+3 q\).