Abrine solution of salt flows at a constant rate of 3 l/min into a large tank that initially held 100 l of pure water. the solution inside the tank is kept well stirred and flows out of the tank at a rate of 2 l/min. if the concentration of salt in the brine entering the tank is 0.4 kg/l, determine the mass of salt in the tank after t min. when will the concentration of salt in the tank reach 0.3 kg/l?