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: the number of the members of a club is more than 50 and less than 80. when 4 people sit at a table, other people exactly divided to 8 - people groups ( 8 people sit at a table. or 7 - people groups ( 7 people sit at a table.. if the members are divided to 9 - people groups, how many people will be left ?
Options: a. 0, b. 2, c. 4, d. 6, e. 8

Ex Output:
d


Ex Input:
Problem: there are 15 balls in a jar. you take out 3 blue balls without putting them back inside, and now the probability of pulling out a blue ball is 1 / 3. how many blue balls were there in the beginning ?
Options: a. 12., b. 9., c. 8., d. 7., e. 6.

Ex Output:
d


Ex Input:
Problem: a person spends 40 % of his salary on food, 25 % on house rent, 15 % on entertainment and 5 % on conveyance. if his savings at the end of the month is rs. 1200, then his salary per month in rupees is :
Options: a. 4000, b. 6000, c. 8000, d. 10000, e. none of these

Ex Output:

c