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: if jack walked 8 miles in 1 hour and 15 minutes, what was his rate of walking in miles per hour ?
Options: a. 4, b. 4.5, c. 6, d. 6.4, e. 15

Ex Output:
d


Ex Input:
Problem: what is the least number of squares tiles required to pave the floor of a room 15.17 m long and 9.02 m broad ?
Options: ['a. 814', 'b. 266', 'c. 287', 'd. 999', 'e. 661']

Ex Output:
a


Ex Input:
Problem: a and b can do a piece of work in 10 days and 10 days respectively. they work together for 10 days and b leaves. in how many days the whole work is completed ?
Options: a. 30 days, b. 40 days, c. 50 days, d. 60 days, e. 70 days

Ex Output:

a