plz solve!!!!!

in the symmetry plane of this system , each point is at the same distance from the two threads

let the distance be r

then the eletric field due to both the threads = λ/2Ï€rε₀

but they will be inclined at 2θ where sinθ=l/2r

so the net electric field will be along the plane=

2cosθ(λ/2Ï€rε₀ )

differentiate it to get maximum

now get the max 'r' .

then find max E.