Four charges are arranged in a square whose edges are $4$ m long. Three

of the charges are $3$ nC $,$ and the fourth charge is to be determined. A charge

of $-2$ nC sits at the center of the square, and the net force on it is $1$xx$10^(-9)$N

toward the fourth charge. What is the fourth charge?

a$)8\mathrm{.}55$ nC

b$)3\mathrm{.}44$ nC

c$)3\mathrm{.}89$ nC

d$)4\mathrm{.}33$ nC

e$)4\mathrm{.}78$ nC

answer is b