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: 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

Output: c

Input: Consider Input: Problem: what number must be added to 6, 16 and 8 to get an average of 13 ?
Options: a. 23, b. 22, c. 44, d. 33, e. 55

Output: b

Input: Consider Input: Problem: a semicircular shaped window has diameter of 63 cm. its perimeter equals
Options: ['a. 162', 'b. 766', 'c. 298', 'd. 277', 'e. 198']
Output: a