6. A tank contains 3000L of water in which 10 kg of salt is dissolved. Brine that contains .7 kg of salt per liter enters the tank at a rate of 20 L/min. The solution is kept thoroughly mixed and drains from the tank at 20 L/min. a.) How much salt is in the tank after 10 minutes? b.) What is the most amount of salt that will be in the tank at any one time