Homework Help: Help with Magnetic Field Questions

1. The problem statement, all variables and given/known data
Two long, parallel wires are attracted to each other by a force per unit length of 335 µN/m when are separated by a vertical distance of 0.460 m. The current in the upper wire is 20.0 A to the right. Determine the location of the line in the plane of the two wires along which the total magnetic field is zero.
m

unknown data is i2

2. Relevant equations

F/l = i1 * i2 * u) / (2pi * d)

3. The attempt at a solution
The farthest I can get with this problem is solving for i2. I have no idea where to go after that. Don't know where to go with finding the location where the magnetic field is zero.
i2 = f/l / (i1 * u) * 2pi * d