Larry, a chemistry student, needs 10% acetic acid solution for a chemistry experiment. He realizes he only has 5% and 20% acetic acid solutions available. He decides to make the 10% solution by combining the 5% and 20% solutions. How many liters of the 5% solution must he add to 8 liters of the 20% solution to get a solution that is 10% acetic acid?
a) 16.5
b) 32
c) 16
d) 8.5
e) 24