Group 1 - UnitedHealth Group's shares experienced a significant rebound, closing at $304.01, up nearly 12% for the day and 20% for the week [1] - The rally was driven by a regulatory filing revealing that Berkshire Hathaway acquired approximately 5 million shares of UnitedHealth, valued at about $1.57 billion [3] - Recent stock purchases by members of Congress, particularly Representative Tim Moore and Representative Marjorie Taylor Greene, occurred just before the stock's rally, raising concerns about potential insider trading [4][6] Group 2 - UnitedHealth has faced challenges including leadership changes and the suspension of financial guidance, while also cooperating with federal investigations related to its Medicare Advantage business [8] - Despite these challenges, UnitedHealth remains the largest provider of Medicare Advantage plans, covering over 8 million individuals, and its Optum division continues to grow in care and technology services [9]