A parallel -plate capacitor of area `A`, plate separation `d` and capacitance `C` is filled with four dielectric materials having dielectric constant `k_(1), k_(2), k_(3)` and `k_(4)` as shown in the figure below. If a single dielectric materical is to be used to have the same capacitance `C` in this capacitor, then its dielectric constant `k` is given by

Options

A. `k = k_(1) +k_(2) +k_(3) +3k_(4)`
B. `k = (2)/(3) (k_(1)=k_(2) +k_(3)) +2k_(4)`
C. `(2)/(k) = (3)/(k_(1)+k_(2)+k_(3)) +(1)/(k_(4))`
D. `(1)/(k) = (1)/(k_(1)) +(1)/(k_(2)) +(1)/(k_(3)) +(3)/(2k_(4))`