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.

Ex Input:
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

Ex Output:
Option D

Ex Input:
Question: In a certain school, the ratio of boys to girls is 5 to 13. If there are 160 more girls than boys, how many boys are there?

Option A: 100

Option B: 36

Option C: 45

Option D: 72

Option E: 117

Ex Output:
Option A

Ex Input:
Question: If f(x) = -*5 (x^4 - 1)/(x^2), what is f(1/x) in terms of f(x)?

Option A: f(x

Option B: -f(x

Option C: 1/f(x

Option D: 5f(x

Option E: 2*f(x

Ex Output:
Option D