An infinite planar slab of thickness \(d\) is aligned parallel to the \(yz\)-plane between \(x = 0\) and \(x = d\). The slab contains a non-uniform volume charge density \(\rho(x) = \rho_0 \sin\left(\dfrac{\pi x}{d}\right)\) for \(0 \le x \le d\), where \(\rho_0\) is a positive constant. Which of the following expressions gives the \(x\)-component of the electric field, \(E_x(x)\), inside the slab as a function of position \(x\) for \(0 \le x \le d\)?