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: On an order of 5 dozen boxes of a consumer product, a retailer receives an extra dozen free. This is equivalent to allowing him a discount of:

Option A: 15%

Option B: 16 1/6%

Option C: 16 2/3%

Option D: 20%

Option E: 30%
[A]: Option C

[Q]: Question: A boy and a girl appear for an interview against 2 vacant posts in an office. The probability of the boy's selection is 1/5 and that of the girl's selection is 1/3. What is the probability that only 1 of them is selected?

Option A: 1/3

Option B: 2/5

Option C: 3/5

Option D: 4/7

Option E: 5/9
[A]: Option B

[Q]: Question: Two trains 190 m and 160 m long run at the speed of 60 km/hr and 40 km/hr respectively in opposite directions on parallel tracks. The time which they take to cross each other is?

Option A: 10.6 sec

Option B: 18.8 sec

Option C: 14.6 sec

Option D: 10.8 sec

Option E: 12.6 sec
[A]:
Option E