Mr. Buffett's Berkshire Hathaway Inc. agreed last week to provide $4.4 billion to help finance the $23-billion deal and to pay another $2.1 billion for an equity stake in the gum company once it becomes a subsidiary of McLean, Va.-based Mars. The companies didn't disclose the exact size of Mr. Buffett's stake but said it's more than 10% and less than a majority of Wrigley's shares.