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: a trader mixes 80 kg of tea at 15 per kg with 20 kg of tea at cost price of 20 per kg. in order to earn a profit of 25 %, what should be the sale price of the mixed tea ?
Options: a. 23.75, b. 22, c. 20, d. 19.20, e. none of these

Ex Output:
c

Ex Input:
Problem: the product of two positive integers is 675 and their difference is 2. what is the bigger number ?
Options: a. 21, b. 23, c. 25, d. 27, e. 29

Ex Output:
d

Ex Input:
Problem: a, b and c started a business by investing rs. 800 / -, rs. 1000 / - and rs. 1200 / - respectively for two years. total profit is rs. 1000 / -. find the c ' s share ?
Options: a. rs. 600, b. rs. 500, c. rs. 400, d. rs. 800, e. rs. 900

Ex Output:
c