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: a person crosses a 800 m long street in 5 minutes. what is his speed in km per hour ?
Options: a. 1.23, b. 2.86, c. 4.36, d. 9.25, e. 9.61
Example Output: e

Example Input: Problem: if x ^ 2 – 3 x = 18, then one possible value of x – 4 =
Options: a. - 9, b. - 5, c. - 3, d. - 1, e. 2
Example Output: e

Example Input: Problem: if n = 2.0423 and n * is the decimal obtained by rounding n to the nearest hundredth, what is the value of n * – n ?
Options: a. - 0.0053, b. - 0.0023, c. 0.0007, d. 0.0047, e. 0.0153
Example Output:
b