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: in what time will a train 50 m long cross an electric pole, it its speed be 360 km / hr ?
Options: a. 0.25, b. 0.5, c. 1.5, d. 2.5, e. 3.5

Ex Output:
b

Ex Input:
Problem: a couple who own an appliance store discover that if they advertise a sales discount of 10 % on every item in the store, at the end of one month the number of total items sold increases 15 %. their gross income from sales for one month increases by what percent ?
Options: a. 1.5 %, b. 2.5 %, c. 3.5 %, d. 4.5 %, e. 5.5 %

Ex Output:
c

Ex Input:
Problem: a man can row 6 kmph in still water. when the river is running at 2 kmph, it takes him 1 hour to row to a place and black. what is the total distance traveled by the man ?
Options: a. 5.32, b. 5.7, c. 5.76, d. 5.74, e. 5.71

Ex Output:
a