Pagpartet is a supermarket that sells good quality products…

Pagpartet is a supermarket that sells good quality products and renders excellent client service. Pagpartet’s membership program for regular clients offers good discounts on perishable products. Its popularity and business generally increase through word-of-mouth. Consumers who shop at Pagpartet rarely switch to another supermarket for their monthly grocery shopping. In the context of marketing, which of the following concepts does this scenario best illustrate?