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: a worker earns $ 20 on the first day and spends $ 15 on the second day. the worker earns $ 20 on the third day and spends $ 15 on the fourth day. if this pattern continues, on which day will the worker first reach a net total of $ 80 ?
Options: a. 24, b. 25, c. 27, d. 30, e. 32

Ex Output:
b


Ex Input:
Problem: a bag contains 10 green and 8 white balls. if two balls are drawn simultaneously, the probability that both are of the same colour is
Options: a. 8 / 15, b. 21 / 44, c. 3 / 5, d. 11 / 15, e. 7 / 15

Ex Output:
b


Ex Input:
Problem: what is the least common multiple of 12,27 and 40
Options: a. 8521, b. 1080, c. 368, d. 8979, e. 6584

Ex Output:

b