I don't understand how the book got the answer of 5/9

The question is:

Given the two terms of the geometric sequence, find the individual term.

t4=5 t8=405 find t2

i used the formula tn = ar^n-1 for this

t8/t4 = 405/5 = ar^7 / ar^3

=81 = ar^4

r=3

5=a(3)^4

5=81a

a = 5/81

t2=(5/81)(3)^1

=5/27