1. The problem statement, all variables and given/known data 2. Relevant equations; 3. The attempt at a solution Here is my thought process and assumptions. Without Vs1 and R2, the open-circuit current would be Vs2/R2, but I know Vs1 and R1 must be contributing in some way. I'm thinking of summing the Voltage sources and using the Potential divider to find Vopen-circuit. Can I do that? I also assume we are calculating the open-circuit current and voltage after transforming into the Thevenin equivalent, not before (is this correct?), even though we are taking the circuit separately and an open-circuit is formed. I know the time constant = RC, since after the Thevenin equivalent, we have RC circuit, driven by VThevenin.