Phillips 66 was up 3.5 percent at $79.97 after Warren Buffett's Berkshire Hathaway disclosed a $4.48 billion stake in the oil refiner.
Utilize the input text as a context reference, choose the right relationship between 'Berkshire Hathaway' and 'Phillips 66' from the options.
Options: parent organization, product/material produced, owner of, chairperson