Final answer:
The question aims to identify the retail price after markup, but the provided context is insufficient to determine the correct option. The examples given relate to changes in quantity demanded with price fluctuations and calculating sales tax, not directly to markup pricing.
Step-by-step explanation:
The question appears to relate to the concept of calculating the retail price after markup, which is pertinent in the context of mathematics, specifically in financial and business math. However, the provided information does not seem to directly answer the question as there is no clear connection with the listed retail prices and the examples given. Instead, the provided information focuses on the percentage change in quantity demanded when a price increases, as well as determining total cost with sales tax included. Unfortunately, this does not allow us to accurately determine which retail price option (A, B, C, or D) corresponds to a specific markup calculation without additional context or information on the original cost and markup percentage.