For removal of a heavy metal from a waste stream by electrodeposition, the electrolyte porosity is anticipated to decrease with time as determined by Faraday's law. For a Pb2+ present at 10mg/liter, given a flow rate of 100 liters/hour, how large must the porous electrode be if it must be used for a minimum of a week before it is replaced. The original porosity is 50%. Assume 99.9% of the lead is removed.