Definition: Given a math problem with context and a question and 5 answer choices, the task is to provide the correct answer choice based on the problem. You must choose one of the given answer choices by letter: a, b, c, d, or e; anything else is invalid.
Input: Problem: a chemical supply company has 60 liters of a 35 % hno 3 solution. how many liters of pure undiluted hno 3 must the chemists add so that the resultant solution is a 50 % solution ?
Options: a. 18, b. 15, c. 20, d. 24, e. 30
Output:
a