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: what is the median of a set of consecutive integers if the sum of nth number from the beginning and nth number from the end is 110 ?
Options: a. 10, b. 25, c. 55, d. 75, e. 100
Example Output: c

Example Input: Problem: the average weight of a group of persons increased from 48 kg to 51 kg, when two persons weighing 78 kg and 93 kg join the group. find the initial number of members in the group ?
Options: a. 87, b. 67, c. 23, d. 75, e. 25
Example Output: c

Example Input: Problem: two numbers are in the ratio of 1: 2. if 6 be added to both, their ratio changes to 3: 5. the greater number is
Options: a. 20, b. 24, c. 28, d. 32, e. 36
Example Output:
b