Calculating how many surplus electrons on each sphere

[hotram]

Homework Statement

Two identical 9.60-g metal spheres (small enough to be treated as particles) are hung from separate 500-mm strings attached to the same nail in a ceiling. Surplus electrons are added to each sphere, and then the spheres are brought into contact with each other and released. Their equilibrium position is such that each string makes a 15.0 ∘ angle with the vertical

How many surplus electrons are on each sphere?

Homework Equations

9.6g=.0096kg
500mm=.5m
F(elec.)=k(Q1)(Q2)/(r^2)
e= -1.602*10^(-19)

The Attempt at a Solution

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I first began by converting all numbers to SI units

Then I found the distance between the 2 balls (not sure)
d=.5sin(15)

charge, I was not sure how to get this to use coulomb so I took the total mass .0096kg/(1.7*10^(-27))= an N

N/2= number of electrons in each ball

And I got lost here.

I do not know how to find charge of objects in this scenario. All I know is they are the same charge because there are repelling

 

[haruspex]

each string makes a 15.0 ∘ angle with the vertical

d=.5sin(15)

Each is at 15 degrees to the vertical. Draw the diagram, and mark the forces acting.