Confused: Determining Net Electrostatic Force and Direction

[aaross]

Could someone please help me figure out how to determine the net electrostatic force and direction in this question?
I have completed what I believe to be the first portion using Coulomb's Law for the force acting on the origin charge (F12 and F13)

A charge of -3.0 micro C is fixed at the center of a compass. Two additional charges are fixed on the circle of the compass (radius = 0.100 m). The charges on the circle are -4.00 micro C at the position due north and +5.00 micro C at the position due east. What is the magnitude and direction of the net electrostatic force acting on the charge at the center? We are asked to specify the direction relative to due east.

Please help!!
--Amanda

[Doc Al]

Each of the two charges on the circle exert a force on the center charge. Find those forces (magnitude and direction) using Coulomb's law. (Perhaps you've done this already.) Now add them, remembering that they are vectors, to find the total force. Hint: find the x and y components, then use some trig to find the total force and the angle it makes.

Show your work and you'll get plenty of help.