A point charge +40.0uC is located on the x axis at the point x = -20.0 cm and a second particle of charge -50uC is placed on the x axis at x = +30.0 cm. What is the magnitude of the total electrostatic force on a third particle of charge -4.0uC placed at the origin. (k = 8.99 x 10^9 Nm^2/C^2) 55.9 N is the answer?