A closed sample switch copies the input to the held node in this final-state model. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
The closed switch copies the input
With the sample switch closed, the input of 4 volts becomes the held value.
Vheld=Vin=4V
The capacitor stores the held voltage
The capacitance is shown as 2 farads, but this lesson claims only the final held voltage.