You are given a math word problem and you are supposed to make use of mathematical concepts like probability, combinatorics, linear equations, sequences/series, or simple operators like addition, subtraction, division, or multiplication to answer the given question. Choose the best option from the 5 given options and report that option.

[Q]: Question: A train 125m long takes 6 sec to cross a man walking at 5kmph in a direction opposite to that of the train. Find the speed of the train?

 Option A: 65kmph

 Option B: 70kmph

 Option C: 75kmph

 Option D: 80kmph

 Option E: 85kmph
[A]: Option B


[Q]: Question: The ratio between the speeds of two trains is 7 : 8. If the second train runs 400 kms in 4 hours, then the speed of the first train is:

 Option A: 70 km/hr

 Option B: 75 km/hr

 Option C: 84 km/hr

 Option D: 87.5 km/hr

 Option E: 88.5 km/hr
[A]: Option D


[Q]: Question: All of the citizens of a country have a six-character or seven-character national identification code that is created using the 26 letters of the alphabet and the 10 digits from 0 to 9. What is the maximum number of citizens who can be designated with these codes?

 Option A: 36^13

 Option B: 35(36^7

 Option C: 37(36^6

 Option D: 35(36^6

 Option E: 37(36^7
[A]:
Option C