Please explain B + C

Mr. Jackson died on June 19 when the total FMV of his property was $23 million and his debts totaled $2.789 million. His executor paid $23,000 funeral expenses and $172,000 accounting and legal fees to settle the estate. Mr. Jackson bequeathed $500,000 to the First Lutheran Church of Milwaukee and $1 million to Western Wisconsin College. He bequeathed his art collection (FMV $6.4 million) to his wife and the residual of his estate to his three children. Assume the taxable year is 2021. Required: a. Compute Mr. Jackson's taxable estate. b. Compute the estate tax payable by Mr. Jackson's executor if Mr. Jackson made no taxable gifts during his lifetime. C. Compute the estate tax payable by Mr. Jackson's executor if Mr. Jackson made a substantial taxable gift in 2011 and used $5 million of his lifetime transfer tax exclusion to reduce the amount on which gift tax was owed to zero. Complete this question by entering your answers in the tabs below. Required A Required B Required C Compute the estate tax payable by Mr. Jackson's executor if Mr. Jackson made no taxable gifts during his lifetime. (Consider intermediate calculations in dollars and not in millions of dollars. Enter your final answer also in dollars and not in millions of dollars.)