The gap between the plates of a parallel-plate capacitor is filled with isotropic dielectric whose permittivity e varies linearly from ex to 2 (2 >

The gap between the plates of a parallel-plate capacitor is filled with isotropic dielectric whose permittivity e varies linearly from ex to ε2 (ε2 > ε1) in the direction perpendicular to the plates. The area of each plate equals S, the separation between the plates is equal to d. Find:
(a) The capacitance of the capacitor;
(b) The space density of the bound charges as a function of if the charge of the capacitor is q and the field E in it is directed toward the growing e values.