The next term is double the previous term, so that the
-th term is given recursively by

This rule tells us that



and so on, with the explicit rule

for
.
If 512 is the
-th term in the sequence, then

It depends on how many options you have
You multiply the total number of books you have time 5 because you can choose 5
2.4+3.06=5.46
5.46+.75=6.21
The answer is 6.21
I think the answer is x=60