The gap between the plates of a parallel plate capacitor of area A and distance between plates d , is filled with a dielectric whose permittivity varies linearly from $\;\in_{1}\;$ at one plate to $\;\in_{2}\;$ at the other .The capacitance of capacitor is :

Question

$(a)\;\large\frac{\in_{0}(\in_{1}+\in_{2})A}{d}\qquad(b)\;\large\frac{\in_{0}(\in_{1}+\in_{2})A}{2d}\qquad(c)\;\large\frac{\in_{0}A}{[d \;ln(\large\frac{\in_{2}}{\in_{1}})]}\qquad(d)\;\large\frac{\in_{0}(\in_{2}-\in_{1})}{[d\; ln(\large\frac{\in_{2}}{\in_{1}})]}$