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.

Input: Consider 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

Output: d


Input: Consider Input: Problem: a merchant marks his goods up by 30 % and then offers a discount of 10 % on the marked price. what % profit does the merchant make after the discount ?
Options: a. 17 %, b. 25 %, c. 69 %, d. 31 %, e. 19 %

Output: a


Input: Consider Input: Problem: by selling an article at rs. 600, a shopkeeper makes a profit of 25 %. at what price should he sell the article so as to make a loss of 25 % ?
Options: a. s. 360, b. s. 480, c. s. 500, d. s. 450, e. s. 550


Output: a