An electrolytic cell is set up to obtain pure copper from an impure rod of copper. The electrolyte solution contains both copper (II) sulfate and sulfuric acid. Impure rod of the copper, Electrode I, contains impurities such as zinc (22%), cobalt (5.8%), silver(2%), gold(1.2%), nickel(1.8%) and iron(12.3%) and inert materials which are non oxidizable. The cell voltage is adjusted so that only copper is deposited on Electrode II. Sludge, which contains some of the solid metal impurities present in the copper rod, forms beneath Electrode I. The other impurities remain in solution as ions. The diagram below represents the cell.

Which one of the following graphs shows the change in mass of Electrode-I over a period of time, starting from the moment the power supply is connected?