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 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%
[EX A]: Option C

[EX Q]: Question: man buys an article for 10% less than its value and sells it for 10% more than its value. His gain or loss percent is?

 Option A: 12

 Option B: 76

 Option C: 26

 Option D: 20

 Option E: 12
[EX A]: Option D

[EX Q]: Question: An elevator starts with 5 pasengers and stops at 8 different floors of the house. Find out the probability of all the 5 passengers alighting at different floors.

 Option A: 90 / 512

 Option B: 105 / 512

 Option C: 15/512

 Option D: 30/512

 Option E: 48/512
[EX A]:
Option B