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.

[Q]: Problem: a is twice as good a work man as b and together they finish the work in 4 days. in how many days a alone can finish the work ?
Options: a. 3, b. 2, c. 7, d. 9, e. 6
[A]: e


[Q]: Problem: when positive integer n is divided by 7, the remainder is 1. when n is divided by 11, the remainder is 5. what is the smallest positive integer k such that k + n is a multiple of 77 ?
Options: a. 2, b. 4, c. 6, d. 8, e. 10
[A]: c


[Q]: Problem: a train running at the speed of 72 km / hr crosses a pole in 9 seconds. find the length of the train.
Options: a. 150 meter, b. 286 meter, c. 180 meter, d. 288 meter, e. 265 meter
[A]:
c