What is the relationship between Steve Ballmer and Microsoft 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.
Text: Twitter rose 4.8 per cent to $US31.15 after Bloomberg reported that former Microsoft chief executive Steve Ballmer owns a 4 per cent stake in the company.
user
employer
assistant