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: 50 % of a number is more than 40 % of 120 by 180. find the number ?
Options: a. 456, b. 480, c. 420, d. 445, e. 320

Ex Output:
a


Ex Input:
Problem: the perimeter of a triangle is 40 cm and the inradius of the triangle is 2.5 cm. what is the area of the triangle ?
Options: a. 87 cm 2, b. 28 cm 2, c. 98 cm 2, d. 26 cm 2, e. 50 cm 2

Ex Output:
e


Ex Input:
Problem: how many seconds will a train 60 meters long take to cross a bridge 120 meters long if the speed of the train is 30 m / sec ?
Options: a. 6 sec, b. 8 sec, c. 15 sec, d. 3 sec, e. 5 sec

Ex Output:

a