What is the relationship between ArcelorMittal and Lakshmi Mittal in the context of the input sentence. Choose an answer from: 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