An RC circuit consists of two identical capacitors C₁ and C₂, in series, a resistor R, a battery with voltage Vᵦ, and two switches S₁ and S₂ initially open, as shown in the diagram. Initially switch S₁ is set to position "B" and then at time 0 the it is moved to position A. At time 0.4 s switch S₁ is moved back to position B and at the same time the switch S₂ is closed. Which of the following graphs correctly represents the measured voltage as a function of time?
[Figure: Circuit diagram with two capacitors in series, resistor, battery, and two switches]
[Multiple choice graphs A through F showing voltage vs time curves]