Utilize the input text as a context reference, choose the right relationship between Costco and retail from the options. Options: product/material produced, manufacturer, distributed by, industry, position held, original broadcaster, owned by, founded by, distribution format, headquarters location, stock exchange, currency, parent organization, chief executive officer, director/manager, owner of, operator, member of, employer, chairperson, platform, subsidiary, legal form, publisher, developer, brand, business division, location of formation, creator.

Secret shoppers for Consumer Reports found that Costco usually offered the lowest retail prices on medications.

Answer: industry