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: 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: the smallest number which when diminished by 2, is divisible by 12, 16, 18, 21 and 28 is
Options: a. 1008, b. 1010, c. 1022, d. 1032, e. 1043

Ex Output:
b

Ex Input:
Problem: the length of the rectangular field is double its width. inside the field there is square shaped pond 6 m long. if the area of the pond is 1 / 8 of the area of the field. what is the length of the field ?
Options: a. 24, b. 32, c. 75, d. 28, e. 11

Ex Output:
a