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.

Example Input: Problem: of the diplomats who attended a summit conference: 20 spoke japanese, 32 did not speak russian and 20 % of the diplomats spoke neither japanese nor russian. if 10 % of the diplomats spoke both japanese and russian, then how many diplomats attended the conference ?
Options: a. 70, b. 96, c. 108, d. 120, e. 150
Example Output: d

Example Input: Problem: what is the sum of natural numbers between 30 and 100
Options: a. 4615, b. 4860, c. 5000, d. 5500, e. 5550
Example Output: a

Example Input: Problem: a certain car can travel 32 kilometers on a liter of fuel. if the fuel tank ’ s contents decrease by 3.9 gallons over a period of 5.7 hours as the car moves at a constant speed, how fast is the car moving, in miles per hour ? ( 1 gallon = 3.8 liters; 1 mile = 1.6 kilometers )
Options: a. 52, b. 65, c. 78, d. 91, e. 104
Example Output:
a