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.

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

Ex Output:
a


Ex Input:
Problem: the average age of a family of 5 members is 20 years. if the age of the youngest member be 10 years then what was the average age of the family at the time of the birth of the youngest member ?
Options: a. 13.5, b. 14, c. 15, d. 12.5, e. none

Ex Output:
d


Ex Input:
Problem: the difference of two numbers is 1415. on dividing the larger number by the smaller, we get 6 as quotient and the 15 as remainder. what is the smaller number ?
Options: a. a. 270, b. b. 280, c. c. 290, d. d. 300, e. e. 310

Ex Output:

b