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 product of two positive integers is 675 and their difference is 2. what is the bigger number ?
Options: a. 21, b. 23, c. 25, d. 27, e. 29

Ex Output:
d

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: find the cost of fencing around a circular field of diameter 32 m at the rate of rs. 2 a meter ?
Options: a. 201, b. 132, c. 772, d. 592, e. 261

Ex Output:
a