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: how many prime numbers are between 76 / 8 and 124 / 5 ?
Options: a. 1, b. 2, c. 3, d. 4, e. 5

Ex Output:
e


Ex Input:
Problem: at 15: 00 there were 22 students in the computer lab. at 15: 03 and every three minutes after that, 3 students entered the lab. if at 15: 10 and every ten minutes after that 8 students left the lab, how many students were in the computer lab at 15: 44 ?
Options: a. 7, b. 14, c. 25, d. 27, e. 32

Ex Output:
e


Ex Input:
Problem: 120 kg of an alloy a is mixed with 180 kg of alloy b. if alloy a has lead and tin in the ratio 2: 3 and alloy b has tin and copper in the ratio 3: 5, then the amount of tin in the new alloy is ?
Options: a. 100.6 kg, b. 120.3 kg, c. 139.5 kg, d. 140.8 kg, e. 114.5 kg

Ex Output:

c