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: by selling 15 pencils for a rupee a man loses 20 %. how many for a rupee should he sell in order to gain 20 % ?
Options: a. 8, b. 7, c. 6, d. 4, e. 10

Ex Output:
e


Ex Input:
Problem: a bag has 9 green balls and 23 pink balls. how many green balls should be added to the bag so that the ratio of green balls and pink balls in the bag becomes 1: 1 ?
Options: a. 10, b. 11, c. 12, d. 13, e. 14

Ex Output:
e


Ex Input:
Problem: the average age of 50 students in a class is 14 years. if the age of teacher is also included, the average becomes 15 years, find the age of the teacher.
Options: a. 30, b. 65, c. 60, d. 55, e. 56

Ex Output:

b