#"The force between two charges is given by formula:"#
#F=k*(q_1*q_2)/r^2#
#r:"distance between two charges"#
#q_1:"the first charge"#
#q_2:"the second charge"#
#F_"AB":" represents the force between charges A and B"#
#F_"CB":"represents the force between charges C and B"#
#F_"AB" and F_"CB" " are opposite forces"#
#F_"AB"=k*((-4)*(-4))/2^2" "F_"AB"=(16*k)/4=4*k#
#F_"CB"=k*((-2)*(-4))/3^2=" "F_"AB"=(8k)/9#
#F_"net"=F_"AB"-F_"CB"#
#F_"net"=4*k-(8*k)/9#
#F_"net"=(36*k-8*k)/9#
#F_"net"=(28*k)/9" "k=9*10^9 #
#F_"net"=(28*cancel(9)*10^9)/cancel(9)#
#F_"net"=28.10^9" N"#