In the context of the input sentence, determine the relationship between 'Berkshire Hathaway' and 'Phillips 66'.
Options: distributed by, subsidiary, owned by, owner of

(Reuters) - Warren Buffett's Berkshire Hathaway Inc (BRKa.N) disclosed a $4.48 billion stake in oil refiner Phillips 66 (PSX.N), rebuilding a bet it had made in the energy industry before oil prices fell.
owner of