condenser numerical???

Question

Two condensers of capacity 4microfarad and 2microfarad are charged to 50V and 100V.These are connected tsuch that likely charged plates are joined together.then the energies stored before and after joining will be in multiples of10^-2 Joule will be
1. 1.33 and 1.5
2. 1.5 and 1.33
3. 2.67 and 3
4. 3 and 2.67

Answer 1

charge = cv
energy = 0.5 cv^2
charge of two capacitors = c1v1 + c2v2 = 4e-6*50 + 2e-6*100 = 0.0004 coulomb
energy of two separated capacitors=.5*c1v1^2 + .5*c2v2^2 = 0.015 J
After connecting the capacitors in parallel, the charge is the same and the voltage = 0.0004/6e-6 = 66.7v
Energy of two paralleled capacitors = 0.5*6e-6*6.67^2 = 0.0133 J
Answer is no. 2.