What is the net force on the -1nC charge in this Coulomb's Law problem?

[Lilian Chan]

Homework Statement

link: https://ibb.co/Xy9s6DR
What is the magnitude of this force?

Homework Equations

Coulomb's Law
Trig equations

The Attempt at a Solution

(.05 m)xcos(60)=0.025m (the distance between the two known charges)
F(between the two known charges)=(9x20^9)(1x10^-9)(10x10^-9)/(0.025)^2=1.44x10^-4
F(that points down)=sin(60)*1.44x10^-4=1.25x10^-4N

The homework system says I got it wrong but I'm not seeing where.

 

[haruspex]

(9x20^9)

9x10^9

F(between the two known charges)

That's only the force between those two charges. The F in the diagram is the net force on the -1nC charge from the other two.