You have a solenoid for which a current \(I\) per winding produces a magnetic field of magnitude \(B_{1}\) inside the soleniod. You cut the solenoid open parallel to its symmetry axis. You then carefully bend it open to form a flat sheet of parallel wires and electrically connect the wire ends on the cut edges in a way that allows you to run the same current through every parallel wire. Now a current \(I\) per wire produces a magnetic field of magnitude \(B_{2}\) just above the sheet. You have a friend who claims that \(B_{1}\) must be many times bigger than \(B_{2}\), because, by cutting the solenoid open, you have allowed the field lines trapped inside the solenoid to escape into an infinite volume. You have another friend who claims that \(B_{1}=B_{2}\), because in both setups, the magnetic field can be determined from Ampère's law using the same rectangular path that encloses the same current. Explain why both friends are wrong.