Two Parallel Conductors Are Carrying Currents in the Same Direction $\mu$

Multiple Choice

Two parallel conductors are carrying currents in the same direction. The currents are non-zero and not necessarily equal. The magnitude of the magnetic field midway between them is 40 $\mu$ T. If one of the currents then has its direction reversed, what is the resulting magnitude of the magnetic field midway between them?

A) It could be any value.
B) 40 $\mu$ T
C) a value less than 40 $\mu$ T
D) a value greater than 40 $\mu$ T