Utilize the input text as a context reference, choose the right relationship between ArcelorMittal and Lakshmi Mittal 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.

He is supported by a very strong leadership team and I am confident he will build on the excellent progress Bill has made in optimising the performance of the asset-base, specifically increasing marketable shipments and reducing costs through debottlenecking and efficiency improvements," Lakshmi Mittal said, also indicating: "I would also like to take this opportunity to thank Bill, who has been a tremendous asset to ArcelorMittal over the past thirteen years and has made a considerable contribution to our company.

Answer: chief_executive_officer