We know that there are (4^9)^5 ⋅ 4^0 at the library, so we just need to simplify this to get the answer.
(4^9)^5 ⋅ 4^0
=(4^9)^5×1
=(4^9)^5
=4^9×5
=4^45. As a result, the total number of books at the library is 4^45 books at the library or B is the final answer. Hope it help!
