Conducting Spheres in Electrostatic Equilibrium

[the-alchemist]

Homework Statement

Homework Equations

potential, V = kq/r where k is 1/4 pi epsilon

conservation of charge, sum of q = Q

The Attempt at a Solution

what i did is let q1 + q2 + q3 = 4*10^-4

then let V1 = V2 = V3 and solve for q3

but i end up getting q3 = 0.0002 which is not the correct ans, which is c, 2.06*10^-4

 

[the-alchemist]

any help? much appreciated!