Two Parallel and Coaxial Current Loops of Radius a Are

Two parallel and coaxial current loops of radius a are placed a distance 2L apart. When you look along the axis at the loops, the current in one is clockwise, and counterclockwise in the other. At a point on the axis half way between the loops the magnetic field in T has magnitude

A) 0.
B) .
C) .
D) .
E) .