Joel and Rachel are both retired. Married for 45 years, they've amassed an estate worth $10.8 million. The couple has no trusts or other types of tax-sheltered assets. If Joel or Rachel dies in 2021, how much federal estate tax would the surviving spouse have to pay, assuming that the estate is taxed at the 40 percent rate? Note: Leave no cells blank - be certain to enter "0" wherever required. Federal estate tax