The topic of this problem is energy storage elements and we're going to work with circuits with switches. The problem is to find the voltage Vc immediately before the switch is thrown at t is equal to 0 and a long time after the switch is thrown at t is equal to infinity. So in order to find these values for V sub c, we have to look at the conditions of interest. First of all, before the switch is thrown, we would redraw the circuit for this condition. The switch is closed at this point. And we know that a capacitor in steady state for a DC circuit that's in steady state, the capacitor acts as an open circuit. So there's no current flowing through the capacitor at t is equal to 0 minus, as long as this circuit has been at steady state for a long period of time. So we still have our resistors R1 and R2, we have our 10 volt source associated with our circuit before the switch is thrown. So if we want to find Vc at t is equal to 0 minus, we simply use voltage division between R1 and R2. Because we know the voltage across this resistor is the same voltage that we're measuring across a capacitor Vc at is equal to 0 minus. So Vc at t is equal to 0 minus is going to be equal to 10 volts, and again, voltage division between the two resistors R1 and R2, in order to find Vc at t is equal to 0 minus. The other condition we want to find is we want to find the voltage Vc at t is equal to infinity. So in order to do that, we have to first of all redraw our circuit for the t is equal to infinity condition. So we have the 10 volt source. Nothing changes with it. It's a constant source for all time. And I have an open circuit here. We still have our R2. And we still have the capacitor, but again, the capacitor's in steady state in a DC circuit and it acts as an open circuit. So this is our Vc at t is equal to infinity. We have R2, we have R1, and we know that we're not going to have any current flow from the 10 volt source to the right-hand side of our circuit, because of our switch that's been opened. So there's no current flowing in this circuit or in this loop either at t is equal to infinity. At this point, the capacitor is completely discharged. Originally had 10 volts times R1 divided by R1 plus R2 across the capacitor. After we open the switch, all that voltage is discharged across R2 until eventually the voltage across the capacitor reduces to 0, because there's no sources over here to keep the capacitor charged. So we go from some nonzero voltage value at t is equal to 0 minus to 0 volts at t is equal to infinity. And the capacitor, we know that the voltage across capacitor cannot change instantaneously. So when we throw the switch at time t is equal to 0, it'll take it a certain amount of time, transient time to go from 10 volts R2 divided by R1 plus R2 to 0 volts at t is equal to infinity.