Electric Force and Field Strength Problem

[reinajonas]

Three charges are located on a coordinate plane scaled off in meters. Charge #1 is 5 nC and located at (0,0). Charge #2 is -3.0 nC and located at (0,-.10). Charge #3 is 6.0 nC and is located at (-3,0).
a) What is the net force (magnitude and direction) on the charge at the origin?
b) What is the electric field strength om the charge at the origin?


I have many ideas as to how I could start this but I'm not quite sure... I think I'm over thinking it. Any help would be much appreciated!

 

[iRaid]

From what I remember don't you have to use:
$$F=\frac{q_{1}q_{2}}{4\pi\varepsilon_{0}r^{2}}$$

For a?

 

[ap123]

The best way to start is by drawing a diagram showing all the charges.
Then draw arrows showing the direction of the forces on the charge at the origin.