Ava and her misfit husband, Frankie, are married and own Blackacre as tenants by the entirety. Ava purchased the property in 1971, four years before they married, for $750,000 and added Frank to the deed of title in 1978. Ava, aged 77, died from pneumonia on January 25, 2021, when the property was worth $9,000,000. How much of Blackacres value must Avas executor include in her gross estate?

a: $0

b: $9,000,000

c: $4,500,000

d: some other amount (your answer:_________________)