A parallel plate capacitor is of area 6 cm$$^2$$ and a separation 3 mm. The gap is filled with three dielectric materials of equal thickness (see figure) with dielectric constant $$K_1 = 10$$, $$K_2 = 12$$ and $$K_3 = 14$$. The dielectric constant of a material which when fully inserted in above capacitor, gives same capacitance would be:

A

4

B

36

C

14

D

12