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.

Example Input: Problem: find value for x from below equation ? x + 1 = - 3
Options: a. 1, b. - 4, c. - 1, d. 2, e. 3
Example Output: b

Example Input: Problem: the average runs scored by a batsman in 30 matches is 50. in the next 15 matches the batsman scored an average of 26 runs. find his average in all the 45 matches ?
Options: a. 31, b. 42, c. 29, d. 97, e. 27
Example Output: b

Example Input: Problem: jerry went to a shop and bought things worth rs. 20, out of which 30 % went on sales tax on taxable purchases. if the tax rate was 6 %, then what was the cost of the tax free items ?
Options: a. 14, b. 14.7, c. 21.3, d. 21.5, e. 21.7
Example Output:
b