The figure shows a parallel-plate capacitor having square plates of edge a and plate-separation d. The gap between the plates is filled with a directrices of dielectric constant k which varies as $\mathrm{K}={\mathrm{K}}_0+\mathrm{\alpha x}$ parallel to an edge as where K and $\alpha$ are constants and x is the distance from the left end. Calculate the capacitance.