a
Coulomb's law states that the magnitude of the electrostatic force between two point charges is directly proportional to the product of the magnitudes of the charges and inversely proportional to the square of the distance between them.

\(F = k \frac{ Q1Q2 }{ r ^2}\)

where \(Q 1\) and \(Q 2\) are the magnitudes of the two charges respectively and \(r\) is the distance between them. The proportionality constant \(k\) is called the electrostatic constant. Each charge experiences a force with the same magnitude and so the ratio of the force exerted by both charges on each other will be \(1: 1\)