Answer: 4.19 N
Explanation: In order to determinate the tension applied on the wire we have to calculate the electric force between the conductor spheres connected by the wire.
As the wire is a conductor the spheres are at same potential so we have:
V1=V2
V1=k*Q1/r1 and V2=k*Q2/r2
where r1=r2, then
Q1=Q2
so the electric force is given by:
F=k*Q^2/d^2 where d is the distance between the spheres.
Finally replacing the values, we have
F=9*10^9(41*10^-6)^2/(1.9)^2= 4.19 N