Two carbon rods are put into a 100.0 mL solution of 2.0 M CuSO4. The electrodes are connected to a power source and turned on. Which of the following needs to be measured in order to calculate the mass of metal that precipitates out of solution?

The current passing to the electrodes and the length of time the current flows
Only the amount of current passing through the electrodes
The voltage difference across the electrodes
The molar concentration of the dissolved ion in solution
Both voltage and current