An infinite conducting slab of thickness \(2d\) is oriented parallel to the \(xz\)-plane and occupies the region \(-d \le y \le d\). A non-uniform volume current flows through the slab in the \(+x\)-direction (out of the page) with current density \(\vec{J} = J_0 \left(\dfrac{|y|}{d}\right)\hat{i}\), where \(J_0\) is a positive constant. Which of the following expressions gives the magnitude of the magnetic field \(B(y)\) as a function of position \(y\) inside the region \(0 \le y \le d\)?