Two small charged spheres are located distance d from each other and experience an electrostatic force of attraction, Fₑ. . If the magnitude of charge of each sphere is tripled and Fₑ is unchanged, what other change must have occurred?
a. The signs of both charges are 1. changed.
b. The sign of only one charge is 2. changed.
c. Distance d was increased by a factor 3. of three.
Distance d was increased by a factor 4. of nine.