Answer:
The correct answer is letter "C": how different customers perceive the value of her services.
Explanation:
Different consumers could value goods or services differently depending on what those products represent for them. The higher the utility of the good or service, the more individuals will be willing to pay for it. This situation could affect or benefit providers being this the reason why most of them have a fixed price on what they offer.
Thus, the reason why some of Henriette's customers pay her different rates is that some of them find her services more valuable than others.