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: one man adds 3 liters of water to 12 liters of milk and another 4 liters of water to 10 liters of milk. what is the ratio of the strengths of milk in 2 mixtures ?
Options: a. 11: 21, b. 15: 33, c. 28: 25, d. 3: 2, e. 31: 33
Output:
c