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 Q]: Problem: a ( 3, w ^ 3 ) is the ( x, y ) coordinate of point located on the parabola y = x ^ 2 - 1. what is the value of w ?
Options: a. 2., b. 4., c. 5., d. 6., e. 9.
[EX A]: a

[EX Q]: Problem: a train of length 250 m crosses a bridge of length 150 m in 20 seconds. what is the speed of train ?
Options: a. 33, b. 27, c. 25, d. 22, e. 72
[EX A]: e

[EX Q]: Problem: 2,7, 17,3, 11,19, 5,13, __
Options: a. 20, b. 21, c. 22, d. 23, e. 24
[EX A]:
d