PHYSICS PLEASE HELP!!!!!!!!!!?

An average family of four uses roughly 1200 L (about 300 gallons) of water per day (1 L = 1000 cm3). How much depth would a lake lose per year if it uniformly covered an area of 53 square kilometers and supplied a local town with a population of 41,000 people? Consider only population uses, and neglect evaporation and so on.