posted by antonio .
please help :/
Three charges are fixed to an xy coordinate system. A charge of +25C is on the y axis at y = +2.7 m. A charge of -16C is at the origin. Lastly, a charge of +66C is on the x axis at x = +2.7 m. Determine (a) the magnitude and (b) direction of the net electrostatic force on the charge at x = +2.7 m. Specify the direction as a positive angle relative to the +x axis.