Two charges $+3$C$+3$C and $+12$C$+12$C are fixed $1$ m apart, with the second one to the right. Find the magnitude and direction of the net force on a $2-$nC charge when placed at the following locations: $($a$)$ halfway between the two $($b$)$ half a meter to the left of the $+3$C$+3$C charge $($c$)$ half a meter above the $+12$C$+12$C charge in a direction perpendicular to the line joining the two fixed charges