At his death in 2011 Nathan owned the following property:
Real estate $ 5,000,000
Cash, stocks & bonds 10,500,000
Personal property 200,000
The real estate is subject to a $1,700,000 mortgage and Nathan made taxable gifts in 2005 totaling $2 million at which time he claimed the maximum unified credit of $345,800 and paid gift tax of $435,000. What is the amount of his estate tax due?