Which of the following correctly describes the section 6166 deferral of estate taxes?

Which of the following correctly describes the section 6166 deferral of estate taxes?

             a. To qualify the value of the closely held business must com at least 50% of the decendent's

             adjusted gross income.

b. Under section 6166 estate tax is displayed for five years and then paid over five equal annual equal installments.

             c. Interest on the deferred tax is calculated based on the fed funds rate.

             d. The deferred tax will be accelerate if the heirs dispose of the business interest.