Three parallel plate capacitors \( C_1 \), \( C_2 \) and \( C_3 \) each of capacitance \( 5\,\mu \mathrm{F} \) are connected as shown in figure. The effective capacitance between points \( A \) and \( B \), when the space between the parallel plates of \( C_1 \) capacitor is filled with a dielectric medium having dielectric constant of \( 4 \), is:
