A$)$ An electric point charge of Q$1=8\mathrm{.}65$ nC is placed at the origin of the real axis. Another point charge of Q$2=4\mathrm{.}99$ nC is placed at a position of p $=2\mathrm{.}12$ m on the real axis. At which position can a third point charge of q $=-1\mathrm{.}66$ nC be placed so that the net electrostatic force on it is zero?

B$)$ Let the sign of Q$2$ be changed from positive to negative. At which position can the point charge q be placed now so that the net electrostatic force on it is zero?