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.

Problem: if a train, travelling at a speed of 90 kmph, crosses a pole in 4 sec, then the length of train is ?
Options: a. 281, b. 125, c. 288, d. 100, e. 121
d

Problem: 4, 12, 48, 240, 1440, 10080,80640 (... )
Options: a. 7620, b. 10080, c. 6200, d. 10020, e. 725760
e

Problem: count the numbers between 10 - 99 which yield a remainder of 5 when divided by 8 and also yield a remainder of 1 when divided by 6 ?
Options: a. one, b. three, c. two, d. five, e. four

e