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: car x began traveling at an average speed of 35 miles per hour. after 72 minutes, car y began traveling at an average speed of 70 miles per hour. when both cars had traveled the same distance, both cars stopped. how many miles did car x travel from the time car y began traveling until both cars stopped ?
Options: a. 15, b. 20, c. 40, d. 42, e. 68

Ex Output:
d


Ex Input:
Problem: the first flight out of phoenix airport had a late departure. if the next 3 flights departed on - time, how many subsequent flights need to depart from phoenix on - time, for the airport ' s on - time departure rate to be higher than 40 % ?
Options: a. 4, b. 6, c. 5, d. 2, e. 8

Ex Output:
d


Ex Input:
Problem: what will be the cost of building to paint which area equal to 196 sq ft, if the price per foot of building is rs. 15 ?
Options: ['a. 120', 'b. 240', 'c. 360', 'd. 380', 'e. 840']

Ex Output:

e