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 in a later tax year.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 is:

A) $0 if Emma died 9 1/2 years after Corey.
B) $300,000 if Emma died 3 years after Corey.
C) $400,000 if Emma died 1 year after Corey.
D) $240,000 if Emma died 5 1/2 years after Corey.
E) The credit as computed is some other amount.