A 500 gallon tank is filled with gasoline containing 10 pounds of a seasonal additive. A gasoline mixture containing 0.02 pounds of additive per gallon is added to the tank at the rate of 50 gallons...

A 500 gallon tank is filled with gasoline containing 10 pounds of a seasonal additive. A gasoline mixture containing 0.02 pounds of additive per gallon is added to the tank at the rate of 50 gallons per minute. The gasoline solution in the tank is continuously and thoroughly mixed and drained out at the same rate of 50 gallons per minute. How many points of additive are in the tank 30 minutes into the operation.