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: Q is as much younger than R as he is older than T. If the sum of the ages of R and T is 50 years, what is definitely the difference between R and Q's age?

Option A: 23

Option B: 28

Option C: 25

Option D: 19

Option E: 11
[A]: Option C

[Q]: Question: Bat is bought for Rs.400 and sold at a gain of 20% find its selling price?

Option A: Rs.320

Option B: Rs.350

Option C: Rs.370

Option D: Rs.480

Option E: None of these
[A]: Option D

[Q]: Question: What is the greatest prime factor of 4^18 - 2^28?

Option A: 2

Option B: 3

Option C: 5

Option D: 7

Option E: 127
[A]:
Option E