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: 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
Example Output: d

Example Input: Problem: the sum of 4 consecutive even numbers is 140. what would be the smallest number ?
Options: a. 32, b. 88, c. 70, d. 123, e. 12
Example Output: a

Example Input: Problem: shekar scored 76, 65, 82, 47 and 85 marks in mathematics, science, social studies, english and biology respectively. what are his average marks ?
Options: a. 71, b. 69, c. 75, d. 85, e. 90
Example Output:
a