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 area of a square field is 625 km 2. how long will it take for a horse to run around at the speed of 25 km / h ?
Options: a. 12 h, b. 10 h, c. 8 h, d. 4 h, e. none of these
Example Output: d

Example Input: Problem: a student took 5 papers in an examination, where the full marks were the same for each paper. his marks in these papers were in the proportion of 6: 7: 8: 9: 10. in all papers together, the candidate obtained 60 % of the total marks then, the number of papers in which he got more than 50 % marks is
Options: a. 1, b. 3, c. 4, d. 5, e. 7
Example Output: c

Example Input: Problem: at a school, 3 - fifths of the male students and two - thirds of the female students speak a foreign language. if the number of males is equal to the number of females, what fraction of the students speak a foreign language ?
Options: a. 17 / 30, b. 19 / 30, c. 11 / 15, d. 7 / 15, e. 2 / 5
Example Output:
b