Effective capacitance of parallel combination of two capacitors C1 and C2 is 10 µF. When these capacitors are individually connected to a voltage source of 1V, the energy stored in the capacitor C2 is 4 times that of C1. If these capacitors are connected in series, their effective capacitance will be :
(1) 3.2 µF
(2) 8.4 µF
(3) 1.6 µF
(4) 4.2 µF