So the equivalent capacitance of the network shown is 4µF
Pd = 100V
E = 1/2CV² = 1/2 × (100)² × 4 × 10⁻⁶
E = 0.5 × 10⁴ × 4 × 10⁻⁶
E = 2 × 10⁻² Joules