David Collins died during the current year. The personal representative of David's estate reviewed the following assets: 1) Stocks in David's name only: $ 2,000,000 2) Investment property in a trust that David has the right to revoke: $1,500,000 3) Primary home owned jointly with his wife (wife did not contribute to the purchase): $1,000,000 4) Insurance policy owned/insuring David with the proceeds payable to his daughter: $800,000 5) Vacation home owned jointly with his son (son did not contribute to the purchase): 5500,000 6) Cash placed in an irrevocable trust by David 8 years ago with David's friend as trustee: 5600,000 What is the value of David's gross estate for estate tax purposes