A parallel plate capacitor with plate area A and plate separation d is filed with a dielectric material of dielectric constant K = 4. The thickness of the dielectric material is x, where \(x < d\). Let C1 and C2 be the capacitance of the system for \(x=\frac{1}{3d}\) and \(x=\frac{2d}{3}\), respectively. If \(C_1 = 2μF\), the value of C2 is __________μF.