RC circuit and kirchoff's loop rule

[okgo]

http://www.screencast.com/users/trinhn812/folders/Jing/media/de5edaba-e848-47f5-82b9-bd770b216e95

I need help with Question 27 specifically. The correct answer is A, but I don't understand why.

I thought it would be B according to Korkoff's Loop rule of the inner left loop, where current of inner left loop is 0 after switch is closed after a long time. So V(battery) - Q/C = 0 so V(battery) =Q/C

 

[Mindscrape]

Let's see here, it can't be a because the cap isn't in parallel with the battery. A capacitor has infinite impedance at DC, so after an infinite time it can be modeled as an open circuit.

So loop 1)
Vb-Vc-IR=0
Loop 2)
Vb-2IR=0

combine to get
Vb-Vc-Vb/2=0

so
Vc=Vb/2

Vc=Q/C

so Vb/2=Q/C

Q=C*Vb/2

Voila.