



$(a)$ Shape of loop
$(b)$ Area of loop.
$(c)$ Current in loop
$(d)$ External magnetic field.



$(A)$ $\vec{B}(x, y)$ is perpendicular to the $x y$-plane at any point in the plane
$(B)$ $|\vec{B}(x, y)|$ depends on $x$ and $y$ only through the radial distance $r=\sqrt{x^2+y^2}$
$(C)$ $|\vec{B}(x, y)|$ is non-zero at all points for $r$
$(D)$ $\vec{B}(x, y)$ points normally outward from the $x y$-plane for all the points between the two loops