A very long line of charge with a linear charge density, λ, is parallel to another very long line of charge with a linear charge density, −9λ. Both lines are parallel to the y axis, and are the same distance r from the y axis, where the first wire is to the left of the origin and the second is to the right. Use Gauss's law and the principle of superposition to find an expression for the magnitude of the electric field at the origin.