Pursuant to Corey's Will,Emma (Corey's Sister) Inherits His Property

Pursuant to Corey's will,Emma (Corey's sister) inherits his property.Emma dies later.The estate tax attributable to the inclusion of the property in Corey's gross estate was $300,000.The estate tax attributable to the inclusion of the property in Emma's gross estate is $400,000.Emma's credit for the tax on prior transfers (under § 2013) is:

A) $0 if Emma died 9 1/2 years after Corey.
B) $32,000 if Emma died 3 years after Corey.
C) $40,000 if Emma died 1 year after Corey.
D) $24,000 if Emma died 5 1/2 years after Corey.
E) None of the above amounts is correct.