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: car x began traveling at an average speed of 35 miles per hour. after 72 minutes, car y began traveling at an average speed of 70 miles per hour. when both cars had traveled the same distance, both cars stopped. how many miles did car x travel from the time car y began traveling until both cars stopped ?
Options: a. 15, b. 20, c. 40, d. 42, e. 68
[A]: d


[Q]: Problem: a student took 5 papers in an examination, where the full marks were the same for each paper. his marks in these papers were in the proportion of 6: 7: 8: 9: 10. in all papers together, the candidate obtained 60 % of the total marks then, the number of papers in which he got more than 50 % marks is
Options: a. 1, b. 3, c. 4, d. 5, e. 7
[A]: c


[Q]: Problem: in what time will two trains cross each other completely, which are running on the same parallel lines in opposite directions, each train running with a speed of 90 kmph being 160 m and 140 m in length respectively ?
Options: a. 5.6 sec, b. 6.2 sec, c. 6.0 sec, d. 7.2 sec, e. 6.8 sec
[A]:
c