Bart and Lisa decide to open a Lemonade Stand. Bart puts 2 pounds of sugar into 4 gallons of water. Unfortunately, he was only supposed to add 1 pound. They cannot just make another batch because they have no more sugar, and do not have any money to buy more. (They spent their last money on the 2-pound bag of sugar.) Lisa rigs a mixing tank (out of the water cooler that they are using) to flush the excess sugar out of the water. She uses the hose to pump water into the tank at a rate of 2 gallons per minute. The mixture flows out at the same rate.Find an equation to determine the amount of sugar in the tank at any given time.