Chandra has 5 liters of a 56% solution of sodium hydroxide in a container. What is the amount and concentration of sodium hydroxide solution she must add to this in order to end up with 7 liters of 46% solution?
◦ 2 liters of 22% solution
◦ 2 liters of 24% solution
◦ 2 liters of 19% solution
◦ 2 liters of 21% solution