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: in what time will a train 120 m long cross an electric pole, it its speed be 121 km / hr ?
Options: a. 2.5, b. 2.7, c. 2.9, d. 3.6, e. 2.1
Example Output: d

Example Input: Problem: the sum of all the integers a such that - 26 < a < 24 is
Options: a. 0, b. - 2, c. - 25, d. - 49, e. - 51
Example Output: d

Example Input: Problem: a " palindromic integer " is an integer that remains the same when its digits are reversed. so, for example, 43334 and 516615 are both examples of palindromic integers. how many 6 - digit palindromic integers are both even and greater than 500,000 ?
Options: a. 160, b. 200, c. 240, d. 300, e. 480
Example Output:
b