A charge of +18 mC is on the y axis at y=+3.0 m. A charge of -12 mC is at the origin. A charge of +45 mC is on the x axis at x=+3.0 m.
a. Determine the magnitude of the net electrostatic force on the charge at x=+3.0 m.
b. Find the direction of the force relative to the -x axis.