Please solve as soon as possible

8. A tank with 400 L of beer contains 4 molar alcohol. Beer with 6 molar alcohol is pumped into the tank at a rate of 5 L/min and the mixture is pumped out at the same rate. When the molarity in the tank becomes 6 molar? a) none of the above t=20 min t=20 min t=40 min e t=60 min