Utilize the input text as a context reference, choose the right relationship between GroupM and advertising 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.

That contract is estimated to be worth $15 million to $30 million, and has resulted in 30 blue chip advertising clients in the GroupM portfolio using premium YouTube ads this year.

Answer: industry