Utilize the input text as a context reference, choose the right relationship between Berkshire Hathaway and Warren Buffett 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.

It should come as no surprise that the most popular of these portfolios is that of renowned investor Warren Buffett , CEO of Berkshire Hathaway ( BRK.B ) and one of the richest people in the world.

Answer: director_/_manager