Task: Question Answering
Input (English): Question: A chemical supply company has 60 liters of a 20% HNO3 solution. How many liters of pure undiluted HNO3 must the chemists add so that the resultant solution is a 50% solution?

 Option A: 12

 Option B: 15

 Option C: 20

 Option D: 24

 Option E: 36
Output (English): Option E