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