Instructions: 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 patient is given exactly 750 milliliters of a mixture of two medications daily. medication a contains 40 % pain killer and medication b contains 20 % pain killer. if the patient receives exactly 215 milliliters of pain killer daily, how many milliliters of medication b are in the mixture ?
Options: a. 150, b. 225, c. 325, d. 425, e. 550
Output:
d