Paleontologists believe that fragments of a primate
jawbone unearthed in Burma and estimated at 40 to
44million years old provide evidence of a crucial step
along the evolutionary paththat led to human beings.
(A) at 40to 44million years old provide evidence of
(B) as being 40to 44million years old provides
evidence of
(C) that it is 40 to 44million years old provides
evidence of whatwas
(D) to be 40 to 44million years old provide
evidence of
(E) as 40to 44million years old provides evidence
of whatwas

OA: D

My confusion: why estimate should not be followed with preposition"at"?
e.g. I estimate the damage at 8000 yuan
I don't think there is a problem in this sample sentence in which estimate connects with "at".