Utilize the input text as a context reference, choose the right relationship between Sergio Marchionne and Fiat 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.

UAW President Dennis Williams is seeking ratification of the tentative agreement he reached with Fiat Chrysler Chief Executive Officer Sergio Marchionne so he can move on to Ford Motor Co. and General Motors Co. to seek similar, but more lucrative deals.

Answer: employer