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: | - 2 | ( | - 25 | - | 5 | ) = ? ? source: preparation material mba center
Options: a. 40, b. – 60, c. 60, d. 75, e. 100

Ex Output:
a


Ex Input:
Problem: in what time will a train 120 m long cross an electric pole, it its speed be 121 km / hr ?
Options: a. 2.5, b. 2.7, c. 2.9, d. 3.6, e. 2.1

Ex Output:
d


Ex Input:
Problem: if x ^ 2 + ( 1 / x ^ 2 ) = 6, x ^ 4 + ( 1 / x ^ 4 ) = ?
Options: a. 10, b. 11, c. 12, d. 34, e. 15

Ex Output:

d