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 Q]: Problem: a rope of which a calf is tied is increased from 12 m to 23 m, how much additional grassy ground shall it graze ?
Options: a. 2989, b. 2789, c. 1210, d. 1288, e. 1211
[EX A]: c

[EX Q]: Problem: the product x of two prime numbers is between 17 and 60. if one of the prime numbers is greater than 2 but less than 6 and the other is greater than 13 but less than 25, then x =
Options: a. 18, b. 29, c. 37, d. 44, e. 57
[EX A]: e

[EX Q]: Problem: in an examination, 30 % of total students failed in hindi, 42 % failed in english and 28 % in both. the percentage of these who passed in both the subjects is :
Options: a. 23, b. 37, c. 56, d. 40, e. 81
[EX A]:
c