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.
Refer to the input text as context and select the correct relationship between 'Berkshire Hathaway' and 'Phillips 66' from the available options.
Options: parent organization, chairperson, product/material produced, owner of