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: of the 20 members of a kitchen crew, 17 can use the meat - cutting machine, 18 can use the bread - slicing machine, and 15 can use both machines. if one member is chosen at random, what is the probability that the member chosen will be someone who can not use either machine ?
Options: a. 0, b. 1 / 10, c. 1 / 7, d. 1 / 4, e. 1 / 3
Example Output: a

Example Input: Problem: rajani has to read a book of 445 pages. she has already read the first 157 pages of the book and if she reads 24 pages of the book everyday then how long will she take now to complete the book ?
Options: a. 25 days, b. 20 days, c. 46 days, d. 21 days, e. none of these
Example Output: e

Example Input: Problem: in a certain alphabet, 9 letters contain a dot and a straight line. 24 letters contain a straight line but do not contain a dot. if that alphabet has 40 letters, all of which contain either a dot or a straight line or both, how many letters contain a dot but do not contain a straight line ?
Options: a. 7, b. 8, c. 14, d. 20, e. 28
Example Output:
a