A disc of reduced semiconducting rutile crystal 2 cm in

Question

A disc of reduced semiconducting rutile crystal 2 cm in diameter and 2 mm thick is heated in air for 10 s at 300°C. After cooling, circular electrodes, 1 cm in diameter, are applied symmetrically to the two major surfaces. The chemical diffusion coefficient D~ for the oxidation reaction in reduced single-crystal TiO₂ is given by

Estimate the capacitance value measured between the electrodes