What is the sum of the geometric series in which a1 = 4, r = 3, and an = 324? Hint: cap s sub n equals start fraction a sub one left parenthesis one minus r to the power of n end power right parenthesis over one minus r end fraction comma r ≠ 1, where a1 is the first term and r is the common ratio. (4 points)

Sn = 1,535
Sn = −484
Sn = 971
Sn = 484